This study was conducted to solve the problem of available phosphorus, which is mainly distributed on the soil surface and easily leads to the severe P competition of plant roots in natural environments. The morphological competition strategy of limited P resources in the vertical direction of adjacent Chinese fir roots was studied by measuring the changes in the root biomass and morphology of Chinese fir seedlings under different treatment conditions. The experiment was performed in a greenhouse at Fujian Agriculture and Forestry University using a Chinese fir clone "YANG-020". Specially designed glass pots 10 cm long, 10 cm wide, and 40 cm high were prepared for the P stress and competition simulation. Two seedlings were planted in each pot, except for the control which contained a single seedling in the center of all the pot. All the treatments were performed using three P treatment levels, i.e., no, low, and normal P treatment (0, 6, and 12 mg/kg KH₂PO₄, respectively). The seedlings of each treatment were harvested separately at the prime, interim, and last stages (September 9, October 30, and December 19, 2013, respectively) to determine the shoot biomass, root:shoot ratio, and root biomass, after determining the root length, surface area, mean diameter, and volume increment over the entire experimental period. According to the results, obvious effects of the interactions between the competitive and P treatments were observed on the root morphology (P < 0.05), root length, and the average diameter of root morphology of Chinese fir seedlings. However, no apparent effects of the interactions between the competitive treatment and P supply on the biomass allocation were observed (P > 0.05) in the specific root length of Chinese fir seedlings. Competition in processing Chinese fir root morphology and growth was significantly higher than that of non-competition processing in single plant seedlings, and with increasing stress time, the growth and root morphology tended to increase significantly. In the early stage of stress, the growth at the period at the middle and cessation was obviously higher than that at the onset. Moreover, the competitive treatment of adjacent plants significantly improved the specific root length of the Chinese fir and improved their ability to actively seek P in the root system. The root surface area and volume increment generally increased and then tended to decrease with increasing P level in the soil. Compared with non-competition treatment, the biomass accumulation of Chinese fir was not obvious, whereas the root biomass and root:shoot ratio were lower than that of non-competitive single seedlings were.