This paper states a new steam doping device in the induction pipe of gasoline engine. Installed in NJ-70 automobile engine, the engine's working parameters are measured and analyzed in test. These results will supply a base for further research on steam doping work process. 介绍了一种汽油机掺水蒸汽的新装置,通过在NJ-70车用汽油机上的试验,对发动机的工作参数进行了实测和分析,为进一步研究汽油机掺水蒸汽的工作过程建立了基础。