Abstract: The net primary production of middle-young stands of Pinus Pyunnanensis is not increases with increasing stand age as their biomass. The total amount of the net primary production in the 4-year-old stand is 530.4g/(m2 .a), the 11-year-old stand 1201.0g/(m2.a), the 23-year-old stand 1060.3 g/(m2.a). The percentages of the net production of tree layers in various layers of three stands are the greatest, herb layer second, shrub layer the smallest. The percentage of the net production of tree layer in the 11-year-old stand is the greatest, 23-year-old stand second, 4 -year-old stand the smallest; The percentages of the net production of shrub and herb layers in the 4 -year-old stand are the greatest, 23-year-old stand second, 11-year-old stand the smallest.The net production of needle is the greatest in all organs of tree layers in three stands, stem wood second.

Key words: Pinus yunnanensis