Straw mulching as one of the important water saving measures was adopted in this experiment of pear tree in arid desert area during 1996 to 1998. The results showed that soil water content (SWC) in a depth of 0 to 60 cm was increased by 1.8% to 3.6% with straw mulching. The highest increased SWC occurred in drought season, with its range from 10.3% to 13.6% for treatment while that for CK was under water deficiency. Roots grew strongly and increased to 66 to 88 items/m². The corresponding water content was increased by 1.28% to 2.07% and 0.87% to 1.33%, and water potential by 0.31 MPa to 0.42 MPa and 0.26 MPa to 0.35 MPa in blade and vegetative shoot, respectively. Both chlorophyll content and photosynthetic rate increased by 19.4% and 18.1%, respectively. As a result, fruit growth enhanced and average increment of both fruit length and width increased by 0.07 mm and 0.058 mm respectively. Single fruit weight increased by 17 to 24 g, and the fruit size increased when the number of fruit per tree did not exceed 12% compared with that without straw mulching.