Fire is a crucial disturbance factor in Mongolian pine forest. Under the approach of space for time substitution, competition intensities of trees were explored using the long tradition of distance-dependent competition index in two 1-hm2 fully mapped plots of Mongolian pine forest across a chronosequence of different intervals of time-since-fire, in Hulun Buir sand region, Inner Mongolia, China. Recruits were also estimated using the geostatistics method of kriging in a-1994-burned stand (B94). Our results show that (1) competition intensities of survival components were all significantly lower than those of pre-mortality agents; (2) competition intensities of survival components in B94 were significantly lower than those of corresponding components in B06 (a 2006-burned stand); (3) most recruits inhabited in the gaps triggered by surface fire in B94. Thus, competition intensity would decrease continuously and significantly across the chronosequence. The survival components may have more resources and space to live on due to the diminishments of competition intensities of stems, which are driven by surface fire, a dynamic driving force in the developing process of Mongolian pine forest.