Abstract: The present invention relates to a polishing liquid for CMP and preparation method thereof. 100 parts by weight of the polishing liquid comprises: 0.1 to 50 parts of abrasive, 0.001 to 0.4 part of surfactant, 0.001 to 0.6 part of film former, and 0.05 to 10 parts of pH regulator, and 0.01 to 4 parts of polishing accelerator, and deionized water in balance; and the pH value of the polishing liquid is 9.5 to 12.5. When a GaAs wafer is polished with the polishing liquid of the present invention, various performance indexes such as polishing removal rate, surface roughness and TTV of the polished wafer are excellent, and the polishing liquid is easy to be washed away, does not corrode equipment, and does not introduce harmful metal ions. The polishing liquid of the present invention can be used continuously and circularly for a long period of 6 to 10 hours, which greatly saves resources and reduces the use cost of the polishing liquid.