of HfO2 optical thin film is reported. We believe the main impurity element in thin film comes from t he coating material. The weak absorption and laser induced damage threshold (LID T) of HfO2 thin film are measured to testify the negative-ion element impurities breakdown model. These results indicate that the LIDT would decrease and the absorption of the films would increase with the increase of the content of negative-ion element. The main reason is the negative-ion elements become th e center of volatile gas source and form defects, which in turn become the cente r of absorption during laser irradiation. So negative-ion elements are harmful i mpurities, their existence will speed up the damage of the thin film.