Abstract: ¹³³Ba is an EC-decay γ-ray source nuclide, which is often used in the calibration of HPGe-γ spectrometer. With the rapid increase in demand for radioactive activity measurement in recent years, it is necessary to establish a fast and accurate ¹³³Ba activity measurement method. Using 4πβ(PC)-γ(NaI) coincidence activity standard measurement device, 4πγ well-type NaI activity measurement device and 4πγ high pressure ionization chamber, the ¹³³Ba activity measurement method was studied to confirm whether the 4πγ activity measurement device, which is calibrated passively by MC simulation, can be used to measure the specific activity of ¹³³Ba solution. The specific activity of ¹³³Ba solution was measured by the 4πβ-γ coincidence activity standard measurement device, and the reference value obtained was 614.0 kBq/g, with a relative expanded uncertainty (k=2) of 1.5%. Based on MC simulation, the detection efficiency of ¹³³Ba point source by 4πγ well-type NaI activity measurement device is 98.5%, and the measured value of specific activity of ¹³³Ba solution was 606.1 kBq/g, with a relative expanded uncertainty (k=2) of 0.93%. Based on the standard values from the NPL, the specific activity verified value of ¹³³Ba solution given by a 4πγ high-pressure ionization chamber was 611.0 kBq/g, with a relative expanded uncertainty (k=2) of 1.3%. The |E_n| of the measured value and the verified value are 0.73 and 0.25 respectively, both of which are less than 1. It can be considered that the results of all three measurement methods were consistent within the uncertainty range. Therefore, it is feasible and reliable to get the specific activity value of ¹³³Ba solution by using the passive efficiency calibration based on MC simulation combine with the 4πγ well-type NaI activity measurement device, which can avoid the complicated process of film sources preparation and efficiency data extrapolation which are necessary for the 4πβ-γ coincidence activity standard measurement device.