Abstract: Taking arsenic (As)-contaminated paddy soil as test object, and by using high performance liquid chromatography inductively coupled plasma-mass spectrometry (HPLC-ICPMS), this paper studied the variations of As species in soil solution when the soil was sterilized or nonsterilized and incubated at different temperatures (5, 27, and 50 ℃) under flooding. In the soil solution (pore water), only As^Ⅲ(arsenite), As^V (arsenate), and DMA^V (dimethylarsinic acid) were detected, but no  MMA^V (mono methylarsinic acid) was found. With the increasing time of flooding and at the test temperatures, arsenite became the predominant species, averagely accounting for 64%, followed by  As^V, with the proportion of 35%, and DMA^V, with the least proportion of 1%. Soil sterilization or nonsterilization had less effect on the concentrations of As^Ⅲ and DMA^V in the soil solution, but remarkably affected the reduction of As^V and the methylation of As^Ⅲ. The promotion effect of soil sterilization decreased gradually with the increasing time of flooding and incubation. At 50 ℃ and after flooded for 23 days, the DMA^V concentration in sterilized soil solution was the highest and up to 23.7 ng·mL^-1, indicating that some thermophilic microbes remained in sterilized soil became predominant species, and promoted the methylation of As^Ⅲ. In sum, the total arsenic concentration in nonsterilized soil at incubation temperature 27 ℃ and flooded for 23 days was relatively low (501 ng·mL^-1), and thus, in As-contaminated paddy rice planting areas, to adopt the water management mode of short cycle flooding-nonflooding could decrease the As level in soil solution as far as possible, and in the same time, save water resources and ensure yielding.