Abstract: A methanol injection system is installed on a non-road common-rail diesel engine to realize the methanol/diesel dual-fuel combustion mode. Based on the non-road China-Ⅳ regulation Non-Road Steady Cycle (NRSC) test conditions, the emission characteristics of pure diesel mode and dual-fuel mode were comparative studied by using exhaust gas analyzer and FTIR. And the conversion efficiency of DOC+DPF+SCR post-treatment system on the dual-fuel engine exhaust emissions was systematically analyzed. The results show that the NO_x and Soot emissions of methanol/diesel dual-fuel combustion mode are significantly lower than those of pure diesel mode, while the CO, HC, methanol and formaldehyde emissions are higher than those of pure diesel mode. After the post-treatment system, the conversion efficiency of CO and HC emissions is higher than 99%. Meanwhile, the conversion efficiency of NO_x and Soot emissions is 84% and 90%, respectively. The methanol and formaldehyde emissions of dual-fuel mode can be oxidized efficiently, and the average efficiency is more than 90%. NRSC test results show that the CO, HC, NO_x and PM specific emission indexes of dual-fuel engine equipped with DOC+DPF+SCR are lower than the limits of non-road China-Ⅳ and Euro-V regulations.