Abstract: The understory shrub and herbs in three forest types, including Pinus tabulaeformis forest, Quercus variabilis forest and mixed coniferous forest in Beijing Forestry University Experimental Forest farm of Miaofengshan, were selected as the research objects. The shrub layer biomass were studied by the method of model and the herb layer biomass were studied by the method of sample. Biomass models were constructed for different organs and the whole plant of species widely distributed in the shrub layer using product of base diameter and plant height (DH), product of the square of base diameter and plant height (D²H), tree crown area (A),volume (V) as the independent variables, then the biomasses of species of shrubs of different forest types were evaluated by selecting the optimal models with largest coefficient of determination and the smallest estimated standard deviation; Herb layer biomasses were calculated by the method of harvesting all quadrat. The results showed that the optimal biomass models for different organs and the whole plant of a single species is that cubic equations is the largest in all models, that is cubic equations>power function>quadratic>linear. The independent variables suitable for the optimal models is that V is the largest in all variables,that is V>D²H>DH>A. The biomasses of shrub and herbs layer varied significantly among different forest types.The shrub layer biomass of three forest: P. tabulaeformis forest>Q. variabilis forest>mixed coniferous forest; The herb layer biomass of three forest: mixed coniferous forest>Q. variabilis forest>P. tabulaeformis forest; The total biomass of shrub and herb layers: mixed coniferous forest>Q. variabilis forest>P.tabulaeformis forest; The proportional distribution of organ of shrub is that trunk and root is larger than branch and leaf, aboveground biomass is greater than the below-ground biomass of herb layer, and shrub biomass>herb layer biomass.