In this study, several equations are employed to estimate monthly mean daily diffuse solar radiation for eight typical meteorological stations in China. Estimated values are compared with measured values in terms of statistical error tests such as mean percentage error (MPE). mean bias error (MBE), root mean square error (RMSE). All the models fit the data adequately and can be used to estimate monthly mean daily diffuse solar radiation from global solar radiation and sunshine hours. This study finds that the quadratic model performed better than the other models: (H) over bar (d)/(H) over bar (g) = 0.945 - 0.675 (H) over bar (g)/(H) over bar (0) -0.166 ((H) over bar (g)/(H) over bar (o))(2) -0.173(S/S(o)) -0.079(S/S(o))(2) The measured values of monthly mean daily diffuse solar radiation for Kashi. Geermu, Shenyang. Chengdu and Zhengzhou stations are analyzed to test the generalization of the selected model. The model is found to be able to predict the measured data with good accuracy. Therefore, it is possible to estimate monthly mean daily diffuse solar radiation by using this equation. (C) 2009 Elsevier Ltd. All rights reserved.