The invention provides a fresh water acclimatization culture method of a mangrove plant, comprising acclimatization culture steps as follows: selection of well-developed Aegiceras corniculatum embryo, saline soaking processing with salinity of 2 per thousand, planting of the processed Aegiceras corniculatum embryo in a seedling culture bed and fresh water acclimatization culture for the planted Aegiceras corniculatum according to the set cycle and salinity gradient. By utilizing the method for fresh water acclimatization culture of the Aegiceras corniculatum of the mangrove plant, the survival rate can reach up to over 90%, the Aegiceras corniculatum of the mangrove plant after acclimatization can grow under the environment of light salt brine and completely fresh water and is suitable to be planted under wetland environment of lake, reservoir and estuary lake and reservoir and estuary, and the Aegiceras corniculatum of the mangrove plant plays an important role in soil and water ecological conservation of fresh water wetland systems.