The invention relates to a preparation method of colored regenerated polyester DTY filaments. The method includes the steps of (1) smashing waste polyester to obtain waste polyester shreds; (2) adopting an RGB ternary color matching method for conducting coarse color matching on the waste polyester shreds to obtain a product I; (3) adding the product I into an alcohol liquid containing a catalystto conduct degradation for generating monomers and/or oligomers; (4) conducting separation and purification on the monomers and/or oligomers and then triggering a polymerization reaction to generate apolymer melt; (5) adopting the RGB ternary color matching method for conducting precise color matching on the polymer melt to obtain a product II; (6) conducting spinning on the product II to obtainthe colored regenerated polyester DTY filaments. The preparation method overcomes the defects such as poor manual color matching stability, low accuracy and large consumption of time and labor in theprior art; by adopting the RGB ternary color matching method, online automatic color matching compensation is achieved during production of colored polyester, the stability and accuracy of polyester color matching are improved, and the application prospect is great.