The invention provides a synthesis process of low-chroma polyester polyols, which includes the following steps: A) under the condition of inert gas protection, esterification of polyols and polyacid or polyanhydride is carried out at 140-215 C, and dehydration is carried out at the same time; B) when the acid value of the reaction system is reduced to below 20 mg KOH/g, catalyst is added; The esterification reaction is carried out at 215-230 (?) C) until the acid value of the reaction system is reduced to less than 2 mg KOH/g, the pressure of the reaction system is reduced from normal pressure to less than 0.01 MPa, and the low-chroma polyester polyols are obtained by vacuum dewatering. The chroma of the low-chroma polyester polyols is less than APHA10. By adjusting the temperature of each stage in the preparation process of polyester polyols, the synthesis process, the synthesis temperature, the program control, the matching of catalyst and dosage with the temperature program are adjusted, and the chroma of the prepared polyester polyols is very low.