Monthly and diurnal change laws of leaf water potential of four species of Salix matsudana Koidz.,Populus simonii Carr.,Salix psammophila C. Wang et Chang Y. Yang and Artemisia desertorum Spreng. in Maowusu sandland and difference in leaf water potential in different crown layers were researched,and correlations of leaf water potential of four species with climatic factors and sap flow velocity were analyzed. The results show that the fluctuation of leaf water potential of S. matsudana,P. simonii and S. psammophila in the morning (5: 00) from May to August is not obvious,but there is a certain difference in leaf water potential of three species at noon (13: 00),in which,the difference in leaf water potential of S. matsudana and P. simonii at noon is not obvious,while leaf water potential of S. psammophila in July and August is obviously smaller than that in May and June. In general,leaf water potential of three species at noon in all months is obviously smaller than that in the morning. Diurnal change curve of leaf water potential of four species tested is mainsingle peak type,the highest value appears from 5: 00 to 6: 00,and the lowest value appears from 12: 00 to 16: 00. Average leaf water potential of S. psammophila in the daytime is the smallest,while there is no obvious difference in average leaf water potential among other three species. In May and August,average leaf water potential of S. psammophila is - 11. 9 and - 17. 1 MPa,respectively,while that of S. matsudana,P. simonii and A. desertorum is - 6. 2 and - 7. 1,- 7. 7 and - 7. 3,- 6. 8 and - 8. 4 MPa,respectively,but that of four species in the nighttime has no obvious change. Leaf water potential of four species all appears the trend of high in lower layer and low in upper layer of crown during the daytime,while leaf water potential almost is the same in upper and lower crowns during the nighttime. The correlation analysis result shows that leaf water potential of four species has negative correlation with air temperature,net radiation and sap flow velocity,and has positive correlation with air relative humidity,in which correlations of leaf water potential of four species in different months with net radiation and sap flow velocity are obviously significant (P < 0. 01). It is suggested that leaf water potential of different species in Maowusu sandland changes with species,seasons and climatic conditions,while in general,net radiation is the most important climatic factor affecting change in leaf water potential of four species.