The straw ash was taken to test the improvement of Shanghai alluvial soil.Aaccording to the different soil volume ratios of straw ash to soil ,the paper studied the influence of rice straw ash on stable aggregate content, consistency index and compaction performance of Shanghai alluvial soil water. The test results show that straw ash can increase the content of soil water stable aggregates and decrease the content of micro-aggregates, when the ash-soil ratio is 20%, the content of water stable aggregates increase to the maximum;with the increase of straw ash content, plastic limit and plasticity index first increase and then decrease, the liquid limit first decreases and then increases. When the ash-soil ratio is 20%, plasticity index increases to the maximum; with the increase of straw ash content, the optimum water content increases gradually, the maximum dry density decreases gradually. Therefore, as a aquatic soil improvement agent, the straw ash can effectively improve the water stability of aggregates content, consistency index and compaction performance, which is beneficial to the development of green agriculture.