To provide the theoretical basis for reasonable exploitation and sustainable utilization of saline-sodic soil, the changes and distributions of soil enzyme activities as well as their relationships with principal soil environmental factors were investigated in saline sodic soils planted in different planting years (1a, 2a, 3a) under mulch-drip irrigation, while the uncropped saline waste land adjacent to the experiment site was taken as the control (CK). The method of time-space transformation was used in the experiment design. The result showed that the activities of alkaline phosphatase, urease and invertase increased with planting years, increased from 1.29, 0.73, and 7.23 μg/(g·h) respectively of the new bed to 14.5, 4.48, and 158.1 μg/(g·h) respectively of the bed planted for three years; soil alkaline phoshatase and urease activities decreased with increasing lateral distance and soil layer depth to the dripper after soils being planted while the variation of soil invertase activities was not obvious. The distributions of soil enzyme activities in soil profiles under mulch-drip irrigation were like ellipse, and soil enzyme activities increased radially. Relationship between soil enzyme activities and principal soil environmental factors increased as planting years increased. After planting for three years soil available nutrients were the primary factors which influenced soil enzyme activities.