The invention discloses a device for simultaneously measuring uranium, radium, thorium, and potassium by gamma spectroscopy combined with active X-ray fluorescence. The device comprises a gamma energyspectrum detecting system, an active X-ray fluorescent system, and an auxiliary device. The invention has the advantages that the isotope embedding is used to automatically calibrate the energy calibration of a gamma ray detector so as to overcome the spectral drift problem. The invention solves the problem of saturation and leakage counting of the gamma ray detector caused by the gamma ray (energy (0.5 MeV) cumulative effect in a low energy region, and judges whether the radioactive nuclides are present in the strata at the moment. The active X-ray fluorescence enables simultaneous quantification and strata parameter analysis from elements such as Si to U in the strata. The gamma spectroscopy combined with the active X-ray fluorescence improves the analytical accuracy and enables the simultaneous measurement of nuclides such as uranium, thorium, radium, and potassium.