The paper used diatomite to carry out the experiment for two kinds of agricultural soils in Shanghai.According to different diatomite volume ratios,it studied the influence of diatomite on the consistency index, water stable aggregate content and densification performance of calcareous soil and yellow soil. Experiment indicated that the correlation coefficients between diatomite contents with andplastic limit and liquid limit are 0.981* and 0.971* respectively, and the influence of diatomite on plastic limit and liquid limit with the content of toviscosity polymer soil is inversely proportional;Diatomite can dramatically increase the content of macro aggregate with the soil particle size greater than 0.25 mm of two kinds of soils; Diatomite can dramatically improve the optimum water content of two kinds of soils and reduce the maximum dry density, and the correlation coefficients are 0.993* and 0.999** respectively. Therefore, diatomite can improve looseness and water retention performance of agricultural soil in Shanghai region.