Abstract: In this paper standing crop, net production, heat energy and production structure in mixed forest of Piaus masacmiam and Castanopsis fisan of different ages were studied. The results showed: Standing crop, net production, heat energy of the mixed forest are respectively 47. 75%. 112. 99% and 46. 82% higher than those in the pure forest, and these of the trees of P. massoniana in the mixed forest are 6. 82%. 7. 60% and 7. 15% higher than those in the pure forest of P. massoniana. Production structure in mixed forest showed: Scale of the asimilative parts and the unasimila-tive parts of mixed forest are a bit bigger than those of the pure forest. The vertical biomass of mixed forest is distributed better than that of pure forest. So the light can be absorbed fully in the mixed forest. Generally speaking, the mixed forest will increase productivity and improve production structure.