In order to investigate the effects of adding different ratios of ammonium sulfate to compound fertilizers of rotary drum process on the mobility of phosphorus in alkaline soil and the growth of oilseed rape，soil phosphorus visualization was used to observe the diffusion distance of phosphorus in the soil，and its effect on the growth of oilseed rape was evaluated by using a pot experiment. The results showed that the addition of ammonium sulfate in compound fertilizer of rotary drum process significantly improved the diffusion distance of phosphorus in alkaline soil，and the optimum addition ratio was 18.66%–28.00%. Under the condition of the same sulfur content，the diffusion distance of phosphorus in alkaline soil of compound fertilizer with ammonium sulfate as the source of sulfur was better than that of compound fertilizer with potassium sulfate as the source of sulfur. With the increase of ammonium sulfate ratios in compound fertilizer，the leaf fresh weight，leaf dry weight and root dry weight of oilseed rape showed the trend of increasing and then decreasing，and the addition of 18.66% ammonium sulfate in compound fertilizer promoted the growth of small oilseed rape significantly higher than other treatments.The chlorophyll content and root dry weight of small rape treated with ammonium sulfate added to compound fertilizer with the same sulfur content(S 4.51%)were significantly better than those of potassium sulfate compound fertilizer. The test results provided theoretical and technical support for the optimization and upgrading of compound fertilizer products，and had certain scientific value in realizing the efficient use of phosphorus fertilizer.