Cationic gemini surfactant preparation method

The invention belongs to the technical field of surfactants, and provides a method for preparing a cationic gemini surfactant (CH3(CH2)m-N(CH3)2-CH2CH(OH)CH2-N(CH3)2(CH2)nCH3.Cl2) by taking epoxy chloropropane and alkyl dimethyl tertiary amine (CH3-(CH2)n-N(CH3)2, wherein n equals to 7, 9, 11, 13, 15 or 17) as raw materials and taking 2-hydroxyl-1.3-propylidene as a linking group. The method provided by the invention overcomes the defect in the prior art that one extremely excessive material is required for improving the reaction yield, dispenses with separation and purification procedures for a finished product, is short in reaction period, leaves no epoxy chloropropane in the finished product, and is suitable for industrial scale production.