The invention provides a decolorization method and a recovery method of colored waste caustic soda in textile finishing. The present invention sequentially performs primary filtration, air flotation treatment, and ultrafiltration membrane decolorization on the colored waste caustic soda after textile finishing, and successively removes particulate matter, colored suspended matter such as larger fluff and fine fluff, and residual pulp dyes in the colored waste caustic soda after textile finishing, effectively Reduced the chromaticity of waste lye. In the present invention, the decolorized spent caustic soda obtained by the above decolorized method is evaporated and concentrated, and the obtained concentrated lye has low chroma, which can be directly reused for textile finishing; the obtained hot water can also be directly used in the production steps. Experimental results show that after textile finishing colored waste caustic soda is treated by the decolorization method and recovery method provided by the present invention, the content of suspended solids is reduced from 1320 mg / L to 444 mg / L, the chromaticity is reduced from 600 to 400, and the Baume degree is increased by 4°Bé To 17 ~ 25 ° Bé, can be directly used for textile finishing.