Abstract: Using modified gap model ZELIG, the forest dynamics was simulated at Songshan Mountain National Nature Reserve.And the results were showed as the followings:1) the model can reasonably describe the long-term forest succession in a warm temperate zone of north China.Populus davidiana and Betula platyphylla are the pioneer tree species in the succession process.The forests would come to be comparative stable and dominated by Quercus mongolica and Pinus tabulaeformis after 100 years.The two species are mutual increase and decrease, however Q.mongolica is predominating;2) the model can well quantify the composition and biomass of tree species.The simulated results of model were consistent with the observed data.Pioneer species as whole were modeled more exactly than as concrete species.The simulated dynamic trends of forests at Songshan Mountain were showed as the followings:1) different initial status strongly affected the species composition and biomass, although systems would restore the identical status.Succession from Q.mongolica stand restored faster than that from P.tabulaeformis;2) the associated tree species in forest land was stressed evidently;3) the stands which were developed from Q.mongolica stands owned the highest mean of biomass, and those developed from P.tabulaeformis were most stable.Some opinions about how to reserve and restore the forests were derived from the results.