It is very significant for maintaining the optimal soil moisture and soil temperature in the crop field, because that is the important foundation of developing an optimal irrigation system. The environment of reasonable soil moisture and temperature in the field will not only enhance the water use efficiency but also benefit crop growth and increase crop yield, especially for interplanting field with complex crop environments. In the experiments, the interplanting of tomato and corn under mulched drip irrigation were tested in Hetao Irrigation District in 2012. We set up three treatments which are the high irrigation quota (tomato: 180 mm, corn: 270 mm), medium irrigation quota (tomato: 132 mm, corn: 202.5 mm) and low irrigation quota (tomato: 84 mm, corn: 135 mm). The moisture content and soil temperature of different depths of root zone were measured in the middle of bare soil between tomatoes belt (A), the middle of mulched tomato lines (B), the middle of bare soil between tomatoes and corn belt (C), the middle of mulched corn lines (D) and crop growth and yield were observed in different growing seasons. The effects of plastic film, soil moisture and crop shade on soil temperature at different rows and depths of inter-planting were studied by the experiment. The results showed that it had apparent effect of mulch on heat preservation under 15 cm soil depths, but the soil temperatures of whole root zone were influenced by crop shade and soil moisture; The soil temperatures of four horizontal positions were significant variation for different the soil depths (5 cm, 10 cm, 15 cm, 20 cm, 25 cm), and the proper sequence of average soil temperature above 10 cm soil depth in different positions was: C > D > A > B, the one under 10 cm soil depth was: D > B > A > C; The study on distribution of the soil temperature in the interplanting field showed that the maximum variational amplitude of soil temperature appeared at the C position, and it would reach 8.10 ℃; the minimum variational amplitude of soil temperature appeared in the B position, and it was only 4.71 ℃. There was definitely some inverse correlation between the soil temperature and soil moisture above 5 cm soil depth, however direct proportion was observed below 20 cm soil depth. The study also found that there was strong temperature effect in the middle of lines between high and low crops (such as C position) during daytime, and the temperature can influence the crop of two sides, so mulched cultivation has obvious effects for restraining the loss of heat. It is thus clear that the optimal soil water and soil temperature are beneficial to form better soil moisture and temperature environment and high crop yield in the intercropping field under mulched drip irrigation. The study will be very meaningful for drip irrigation farm management in the Northwest Region.