The invention discloses an improved fertilizer for saline and alkaline land and a preparation method of the improved fertilizer. The improved fertilizer for the saline and alkaline land is prepared from the following raw materials in parts by weight: 25-28 parts of maleic anhydride, 15-20 parts of citric acid, 20-30 parts of calcium superphosphate, 10-12 parts of a sodium ion adsorbent, 2-4 parts of a microbial agent, 25-32 parts of fulvic acid, 15-20 parts of a trace element fertilizer, 30-38 parts of a chicken manure fermentation fertilizer, 20-35 parts of peat, 3-5 parts of perlite, 5-8 parts of vermiculite and 20-25 parts of smashed straw particles. The invention further provides the preparation method of the improved fertilizer for the saline and alkaline land. According to the improved fertilizer for the saline and alkaline land, various soil improving measures can be synthesized, effects of reducing salt and alkali for the saline and alkaline land are good, the water content of the soil is high, the water retention property and the fertilizer retention property of the soil are good, besides, the survival rate of planted plants is high, and virtuous cycle of the soil of the saline and alkaline land is realized.