Abstract: Through radiation measurement of in-site system equipment in three types of reactors during overhauling, the typical types of radio-nuclides and the energy range of β ray existed in nuclear power plants (NPPs) were obtained. The surface activity responses to β rays with different energy of some common-used β surface contamination monitors were experimentally investigated. It is found that using the surface activity response of ⁹⁰Sr-⁹⁰Y plane source to calibrate these monitors would underestimate the real level of surface contamination. With respect to the energy range of β ray in NPPs, it is suggested that ²⁰⁴Tl or ³⁶Cl would be employed to calibrate the surface activity response of β surface contamination monitors.