At present, many individual tree competition indices are used to measure the competitive ability of trees, and they are generally divided into distance-independent indices and distance-dependent indices depending on whether one is considering the space between trees. Distance-dependent indices are commonly used, especially the Hegyi competition index (CH). The CH was used to analyze the spatial structure of a Phyllostachys edulis stand studied by Tang et al., but we found that this CH needs to be improved. P. edulis is a Bambusoideae (Gramineae) species and does not have secondary cambium tissue, resulting in the termination of diameter at breast height (DBH) growth after completion of the stem growth. Unfortunately, there are different competitive intensities associated with the spatial structure of P. edulis stands, even in situations where the same distance exists between object and competition bamboo plants. This means they might have the same DBH, but would be considered to be of a different age. Such distinctions cannot be provided by the existing CH. In fact, competition within a P. edulis stand is affected significantly by intensity of physiological activity, which changes with variation of the metabolic turnover and aging process of an individual, or with its material growth period. Material growth periods are divided into enhancement stages, stationary stages, and declining stages, depending on different intensity of physiological activities. In the light of characteristic of P. edulis, considering its metabolic turnover and aging process, and adding a material growth period factor, a new competition index-competition potential (CP), which is based on CH (the Hegyi model), was proposed to analyze the spatial structure of P. edulis stands. A permanent plot measuring 100 m × 100 m, including a relatively lightly disturbed P. edulis stand, was established in the Tianmu Mountain National Nature Reserve, Zhejiang province. There have been five annual surveys of the plot. Each bamboo tree was tallied and its coordinates (X, Y, Z) were measured using a total station survey device. From 2009 to 2013, we used the new competition index, CP, to quantitatively analyze the dynamic competition within the bamboo stand, as well as to study the dynamic relationship between intensity competition and DBH, and the dynamic relationship between intensity competition and age class. The results showed that the P. edulis stand has clear on-year/off-year cycles and that the competitive intensity of on-years (2010, 2012) is obviously higher than that of off-years (2009, 2011, 2013). The difference in competitive intensity within the P. edulis stand between on-years and off-years was significant (P < 0.01). The difference in competitive intensity within the P. edulis stand between on-years was not significant (P > 0.05), as was the difference in competitive intensity between off-years (2011and 2013; P > 0.05). Because of a snow disaster and the emergence of a number of new shoots, the competitive intensity within the P. edulis stand in 2009 showed significance difference (P < 0.01) from other years. The competitive intensity within the P. edulis stand decreased with increasing objective diameter class, and the results showed that the competition had a powerful relationship with DBH. The competitive intensity within the P. edulis stand increased with increasing age class and also had a significantly linear correlation with DBH.A combination of the growth characteristics and adopted physiological characteristics of P. edulis was used to develop an expanded analysis of competition between individuals of P. edulis. This allowed us to develop a more comprehensive and effective model (CP) to describe competition within a P. edulis stand. The new CP is therefore a feasible and reliable way to analyze competition within P. edulis stands and their dynamic characteristics. For these reasons, it could provide a theoretical basis for management of artificial P. edulis stands.