Abstract: UV visible absorption of fourteen type II UV absorbers of benzotriazol structure was tested, and the increase of their molar absorption coefficient and the red shift of their maximum wavelength were due to halogen in their molecule structures. Solubility parameters of ten UV absorbers were calculated. Compatibility of six UV absorbers was also tested. It was found by this test that the introduction of long chain alkyl group improved the UV absorber's compatibility. Photodegradation test proved that UV absorbers could efficiently protect the polymers involved.