Dipotassium salt of 1-nitro-2,2-bismercaptoethylene is the key intermediate which can be used to produce N-methyl-1-methylthio-2-nitroethenamine. The selectivity equations of main and side reactions were developed to analyze the effect of temperature and concentration, and for reducing side-product and enhancing product yield the following improving measures are taken:1) increasing the temperature from 25℃ to 40℃; 2)adding CS_2slowly and dropwisely; 3)diluting the concentration of KOH/C₂H₅OH from 30% to 20%. With adopting new synthesis technology, the product yield increases to over 90%. The new synthesis technology is of potential for industrial-scale production. Current results indicate that, via analyzing the effect of temperature and concentration, then taking correspondent means to adjust and modify the reaction conditions and the feeding fashions, the aim of increasing product yield can be achieved.