The invention discloses a liquid colorant for coloring polyester fiber stock solution. The liquid colorant comprises the following components by weight percent: 65 to 95% of liquid dispersion medium, 3 to 30% of colorant, 2 to 5% of dispersing agent and the like. According to the liquid colorant disclosed by the invention, a pigment or a dye and a liquid carrier are processed by dispersion equipment, such as grinding by a grinding machine and the like; a dispersion degree and a pigment utilization rate are high; the liquid colorant has the advantages of high storage stability, good coloring effect and the like.