The invention provides a method for continuously producing polymercaptan by using micro-channel reactors. The method comprises the following steps: S1) stirring and mixing a mercaptoalcohol compound and an alkal solution in a first micro-channel reactor to obtain a homogeneous mixed solution; S2) introducing the homogeneous mixed solution into a second micro-channel reactor to react with epichlorohydrin in order to obtain a thiopolyol solution; S3) introducing the thiopolyol solution into a third micro-channel reactor to react with an acidic solution of thiourea in order to obtain an isothiourea salt solution; and S4) introducing the isothiourea salt solution into a fourth micro-channel reactor to react with an alkaline hydrolysis reagent in order to obtain polymercaptan. Compared with theprior art, the method has the following advantages: the micro-channel reactors are used for continuous production to achieve the good mass and heat transfer effect and accurately control the reactiontemperature, do generation of impurities is effectively inhibited, the reaction time is shortened, side reactions are further reduced, the product quality is improved, and the purity of downstream products is further improved.