Abstract: In order to solve the problem of cracking of carbon tool steel in quenching, calcium chloride water solutions with different relative densities were used as quenchants.The distortion,hardness and microstructure of quenched specimens were studied.The results indicate that saturated calcium chloride water solution,as a kind of hardening agents,can ensure the hardness of the quenched work piece,reducing the distortion and the cracking of the work piece,which can also improve the quenching quality of the carbon tool steel.