A series of field irrigation experiments of bare plot (BP), plastic film mulched plot(PFP) and corn straw mulched plot(CSP) were conducted during the seasonal freeze-thaw period. The effects of irrigation at different stages on soil temperature and soil freeze-thaw characteristics were analyzed. The results showed that the soil temperatures of plots irrigated earlier in freezing period were lower during the freeze-thaw period. The irrigation had a little effect on the soil temperature of BP and PFP in the thawing period, and the irrigation accelerated the thawing of the surface frozen layer. The soil temperatures of CSP irrigated at thawing period were lower and had a smaller variation. The mulching of corn straw went against soil thawing. The irrigation had a great effect on maximum soil freezing depth in the rapid increasing stage of accumulated negative soil temperature at the depth of 5cm.