A preparation method of methyltinlaurate uses a methyl tin chloride water solution, lauric acid and alkali liquor as main raw materials and is used for one-step synthesis of the methyltinlaurate. The method comprises the following steps that 1, the lauric acid and the methyl tin chloride water solution are put in a reaction kettle, the mixture is heated and stirred, and the alkali liquor is dropwise added when the temperature is up to 50-70 DEG C; 2, the temperature of a reaction system is controlled to be 50-70 DEG C, alkali liquor adding continues in a dropwise mode, and when the pH value of the mixed liquid is up to 4-7, alkali liquor adding is stopped, and standing is performed for phase splitting; 3, an organic phase is taken for washing, and then standing is performed for phase splitting; 4, reduced pressure distillation is conducted on organic matter at the temperature of 60-140 DEG C, water and other low-boiling-point impurities are removed, and then filtration is performed to obtain the methyltinlaurate. Methyl tin oxide and other durst raw materials are not related, lauric acidsaponification is avoided, waste water can be recycled, and the preparation method has the advantages that production equipment is simple, control is easy, the manufacturing cost is low and product quality is stable.