Abstract: The stress-strain state of spot welded low carbon steel structure was studied by three methods including extensometer measurement, tensile test and numerical simulation based on ANSYS software. The relationship between angle distortion and load was obtained. The results proved the reliability of simulated mechanics model of spot welding structure including weld and plastic ring and base metal. The relationship between angle distortion and load was achieved by analyzing simulation results of the spot welding structure mechanical model. The yield limit and plastic modulus were adjusted during simulation to make the simulation result of deformation consistent with that of the test result. The test results indicated that the yield limit and plastic modulus of plastic ring were measurable by finite element simulation method which could provide references for relative research.