Preparation method of 3-methylthiopropionaldehyde

The invention relates to the field of production of 3-methylthiopropionaldehyde, in particular to a preparation method of 3-methylthiopropionaldehyde. According to the invention, water is introduced in synthesis of 3-methylthiopropionaldehyde, wherein AC in MMP is reserved on the upper layer of a system due to absorption of the water on acrolein, the water has an extraction effect, and MMP and MC in the system are layered, so that MC is also reserved on the upper layer of the system; due to the solvation effect of water, the dissociation degree of the catalyst is enhanced, so that the amount of the catalyst can be reduced to be less than half of the original level and still keeps the same reaction rate; and the catalyst can be recovered/partially recovered, the cost is saved, and in the subsequent refining process of MMP, the polymerization degree of MMP is reduced due to reduction of the content of the catalyst; light components removed in the MMP refining process are condensed and absorbed, and MC and MMP a