The invention provides a controlled release fertilizer special for saline alkali soil improvement. The controlled release fertilizer is characterized by being prepared from 25-35 wt% of medical stone, 5-10 wt% of potassium chloride, 5-15 wt% of mineral powder, 25-30 wt% of organic fertilizer and water, and the sum of the all components is 100%; the active solid strains include lactic acid bacteria, bacillus subtilis, bacillus megatherium, trichoderma, aspergillus niger, monascus, trichoderma harzianum, aspergillus aculeatus and yeast; the mineral powder is one or a mixture of peat, zeolite, vermiculite, montmorillonite, calcium carbonate and expanded perlite, the fineness of the mineral powder is less than or equal to 200 meshes, the organic fertilizer contains a fermented manure fertilizer, a rape seed cake fertilizer and straw, and the weight ratio of the fermented manure fertilizer to the rape seed cake fertilizer to the straw is (5-7.5):(2.5-3.5):(0.5-1.5).