The stress state of galvanized steel strand cable for cable-stayed bridge in-service are hard to be detected effectively by existing technologies. In view of this, a method based on electromagnetic non-destructive testing technology was proposed to detect the stress state of galvanized steel strand cable. Controlled tension test was performed on eight galvanized steel strand specimens using universal testing machine. The electromagnetic signals in the tension process were obtained via LCR meter. The variation characteristics of the signals were examined, and the relation between electromagnetic signals and stress state of the specimens was analyzed. Test results illustrated that with the rising of tensile stress σ, the relative magnetic conductivity μ_r of specimens increased at first and then decreased. The peak of μ_r arrived when stress reached 73.29% of tensile strength f_ptk of the specimens. Still with the rising of stress σ, the value of dμ_r/dσ which denotes the gradient of relative magnetic permeability to tensile stress increased at first and then decreased. The peak value of dμ_r/dσ occurred when stress reached 36.07% of tensile strength f_ptk. Besides, while the value of dμ_r/dσ was not less than zero, the stress of specimen was within 73.29% of tensile strength f_ptk. The test verifies the feasibility of detecting the stress of steel strand based on electromagnetic induction technology, and offers a technical reference for future stress detection of galvanized steel strand cable.