A soil culture experiment was conducted to study the effects of two sulfur fertilizers including sulfur and sodium sulfate combined with calcium magnesium phosphate on the changes in Cd availability and the transformation of Cd morphology in paddy soil to investigate the immobilization effect of sulfur fertilizer combined with phosphorus fertilizer on cadmium （Cd） in paddy soil. Six treatments including control （CK）， calcium magnesium phosphate （P）， sulfur （S1）， sodium sulfate （S2）， calcium magnesium phosphate + sulfur （PS1）， and calcium magnesium phosphate + sodium sulfate （PS2） were set up. The relationship between the Cd availability in soil and the available sulfur， available phosphorus， pH， and Eh was analyzed. The results showed that the Cd availability in soil decreased significantly after applying different immobilization materials in the soil. Among them， PS1 treatment had the lowest content of available Cd， which decreased by 49.8% compared to CK. P treatment increased soil pH by 0.39 compared to CK. S1 treatment significantly reduced the soil Eh value， which was 23.2% lower than CK， and promoted the reduction of SO₄^2- to S^2-. PS1 treatment significantly increased the content of available phosphorus in soil. Compared with CK， the available phosphorus in PS1 treatment increased by 81.9%. PS1 treatment synergistically promoted the Cd transformation of exchangeable fraction to residual fraction in soil due to the regulation of soil Eh， available sulfur and available phosphorus. It is indicated that the combination application of sulfur and calcium magnesium phosphate has potential in alleviating Cd pollution in paddy soil.