Abstract: In order to measure the radioactivity of pure beta-emitters, which are low energy, low level and lack of their standard solutions, an efficiency calibration method was developed by scaling the liquid scintillation spectrometer (LSA) with 6 low energy beta-nuclides. On the base of this method, a three-dimension surface on nuclides’ average energy, quenching index and determining efficiency was fitted. Various factors possibly influencing the measurement of LSA were studied, such as scintillation fluids, quenched agents, medium, vials, volumes and so on, and the optimum conditions for LSA were obtained.