After the implementation of gasification process technological transformation project in Tianxi CTG Company of JAMG, the pressure of gas from gasification process is increased from 0.5 MPa to 3.7 MPa，the effective composition of gas（CO+H2） is increased from 60 % to 90 %. In order to adapt to the changes of raw gas parameters, the corresponding optimization and transformation of rectisol system is implemented. After the transformation, the purpose of saving investment is achieved by fully utilizing the existing equipments. Meanwhile, the system cold energy is recovered, the quality of circulating methanol is improved, the system consumption is decreased and the long period stable and safe operation is ensured.