Pinus sylvestris var. mongolica is one of the main native plantation species in Hulunbuir sandy land. The response of net productivity of Pinus sylvestris var. mongolica plantation to changes of climatic factors is important to understand the relation between Pinus sylvestris var. mongolica plantation growth and climate change. Three plots were established with a size of 30 m×30 m in 43-years old Pinus sylvestris var. mongolica plantation in Hulunbuir sandy land. Combining the dendrochronological method and empirical biomass growth equations, the biomass and net primary productivity of Pinus sylvestris var. mongolica plantation in the past 41 years were calculated. And the correlations between net primary productivity and climatic factors were analyzed, including monthly air temperature, humidity and precipitation. The results indicated that the variation of biomass followed the logistic equation as the increasing forest age, and the biomass of the plantation increased from 4.83 t/hm² in 1977 to 167.95 t/hm² in 2017. The net primary productivity showed an inter-annual variation with a trend of increasing first, then decreasing, and finally stabilizing. The net primary productivity of the stand ranged between 2.63 t hm^-2 a^-1 and 6.13 t hm^-2 a^-1 with an average of 4.08 t hm^-2 a^-1. The net primary productivity was closely correlated with climatic factors, but showed a time lag. The net primary productivity of Pinus sylvestris var. mongolica plantation was significantly correlated with the monthly precipitation in August and December of the previous year and that in March of the current year. A positive correlation was found between the net primary productivity and the air relative humidity from August to September in the previous year and the current year. There was negative correlation between net primary productivity and the monthly temperature. In particular, the temperature in June-September of both previous and current year significantly affected the net primary productivity. Generally, the net primary productivity of Pinus sylvestris var. mongolica plantation was affected by temperature and precipitation, but was more sensitive to temperature. It may imply a decrease of the net productivity of the Pinus sylvestris var. mongolica plantations in the future due to possible climate warming in the Hulunbuir sandy land region.