Abstract: Based on the LabSOCS software, studies on the detector efficiency calibration of the ¹³⁷Cs γ-spectrum analysis in the seawater were performed under different aspects of sample compositions, relative geometric positions to the detector, masses and densities.The results revealed that the effects brought by sample compositions and relative positions to the detection efficiency could be ignored.A unit duality quadratic polynomial was employed to describe the relationship between detection efficiency and sample mass as well as density, and the result showed that the multiple correlation coefficient could reach as high as 0.99946.These results have replenished theoretical basis for the ¹³⁷Cs γ-spectrum analysis in the seawater.