Subalpine forest region of Western Sichuan was located in the outer fringe of southeastern Qinghai-Tibet Plateau with high mountains and deep valleys, and was covered with subalpine forests, mainly dark coniferous ones. The forest had been greatly reduced and degraded, as a long-term over-logging on a large scale. Natural secondary coniferous-broadleaved forest was one of the main secondary forest types in subalpine region of Western Sichuan, which was originated from the clear-cutting lands between 1950s-1980s due to the overexploitation of coniferous forests. Additionally, it was an important transitional stage in the secondary succession from cutting-blank to climax community. Our objectives were to quantify the aboveground biomass and aboveground net primary productivity (ANPP) of coniferous-broadleaved forests at different altitude, and to explore whether different response of coniferous species and broadleaf ones to changing altitude was existed or not. Based on the history data of forest management and field survey, we investigated eighteen sample plots of coniferous-broadleaved forests with 40 years old, distributed along four (A: 2900-3050 m; B: 3150-3300 m; C: 3300-3450 m; D: 3450-3550 m) altitudes from 2900 m to 3550 m, all of which were located on the same slope of Jiabi Mountain in Miyaluo forest region. We sampled 4 or 5 plots with similar site conditions and stand factors in each gradient. All tree layer plants (DBH ≥ 5 cm) were surveyed and sorted into two groups: broadleaf species and coniferous species, based on the leaf characters. Aboveground biomass was calculated using allometric relationships of this region summarized by other experts. The ANPP was estimated by the mean annual increment method. The biomass and ANPP of tree layer decreased from 157.07 t/hm2, 3.43 t ?hm-2 ?a-1 to 54.65 t?hm-2, 1.36 t?hm-2 ?a-1 respectively, with increasing elevation. The temperature difference and reducing stand density among altitudes were possibly the main factors affecting the stand biomass and ANPP. Individual biomass and ANPP of broadleaf species decreased from 200.55 kg, 4.96 kg/a at A to 47.86 kg, 1.19 kg/a at D with increasing altitude. However, opposite conclusion was found in coniferous species. The corresponding values of coniferous species increased from 51.57 kg、1.28 kg/a at A to 73.88 kg、1.84 kg/a at D. But there were no significant difference at 0.05 level. This heterogeneity seems to be in part responsible for differences in biological characteristics of species and forest habitat. Correlation analysis revealed that broad-leaf species were more significant and sensitive in response to altitude than coniferous species in this region. The difference of biomass and ANPP between different altitudes may be narrowed down with the global warming.