During April and May in 2010,the primary production in the Xiaojiang River backwater area,Three Gorges Reservoir was measured using the black-white-bottle method.The distribution features and relationships with light intensity,chlorophyll-a concentration(Chl.a),water temperature and partial pressure of carbon dioxide(pCO₂ ) were studied.The results showed that the gross primary productivities(GPP) were 1927.5 mg O₂/(m² ·d) and 1325.0 mg O₂/(m²·d) in April and May,respectively, the average value was 1626.3 mg O₂/(m²·d).The gross respirations(GR) in the two months were 1037.5 mg O₂/(m²·d) and 1062.5 mg O₂/m²·d,respectively,and the average value was 1050.0 mg O₂/(m²·d).The gross net productivities(GNP) in the two months were 890.0 mg O₂/(m²·d) and 262.5 mg O₂/(m²·d),and the average value was 576.3 mg O₂/(m²·d).Ratio of GPP/GR were 1.86 and 1.25.These indexes suggested that the Xiaojiang River was autotrophic in the spring season.Pri-mary productivity(P) in each depth and the ratio of productivity to respiration(P/R) had similar vertical distribution feature, showing that the maximum values occurred near the surface and they decreased with depth.Correlation analysis showed that light intensity(I) and Chl.a were significantly positive correlation with the P.Equations of the linear regression model P with Chl.a and with I were respectively:P=0.154 Chl.a -0.278,with coefficient R2=0.570,and P=0.001I -0.013,with coefficient R²=0.942.