The invention relates to a novel propylene epoxide caustic soda saponifying process. Caustic soda is fed in two levels. One part of caustic soda liquor first enters into a premixer to be mixed with chloropropanol liquor for neutralization reaction, while the other part of caustic soda liquor then enters into the mixer to be mixed with the neutralized chloropropanol liquor, and then enters into a saponifying tower for saponifying reaction. A saponifying tower is a packed tower, and meanwhile, the tower and material are correspondingly changed. According to the novel propylene epoxide caustic soda saponifying process, the caustic soda is used as a saponifying agent, and caustic soda liquor mixed with chloropropanol liquor enters into the special saponifying tower in two levels, and chloropropanol is stripped from the bottom of the tower by steam. The saponifying tower is the packed tower, and meanwhile, the tower and material are optimized. The process can greatly improve the conversion ratio of raw materials and product yield to a great extent. Coarse propylene epoxide with high purity can be obtained on the top of the tower, and meanwhile, the COD (Chemical Oxygen Demand) value of wastewater at the bottom of the tower can be lowered to a great extent.