The invention belongs to the field of chemical engineering, and particularly relates to a continuous flow synthesizing method and a system for methyl 4-chloroacetoacetate without solvent. The method comprises the following steps of in the reaction process, firstly, performing chlorination reaction on diketene and liquid chloride through a micro-channel reactor module 8, and then performing esterification reaction on the chlorinating liquid and methyl alcohol through a reaction module 13, so as to obtain a crude product of the methyl 4-chloroacetoacetate; performing pressure-relief rectification on the crude product, so as to obtain a finished product of the methyl 4-chloroacetoacetate. The method can solve the problem that because the micro-channel reactor has certain drag, the liquid chloride cannot be fed by a conventional feeding device; in the micro-channel reactor, the mixing effect of gas and liquid reaction is poorer than the mixing effect of liquid and liquid reaction, the metering accuracy of gas is poor, the amount of reaction byproducts is increased, the yield rate is reduced, and the like.