There is nonlinear relation between the weighing sensor′ s output and input, which is caused by the structure characteristics of the elastomer, thus affecting the accuracy of the weighing sensor. This paper launched the analysis of the nonlinear error caused by the large deformation of elastomer. By using the finite element analysis method, this paper obtained the relative error caused by the large deformation of elastomer in the 0~3 kg range through quantitative analysis, and the corresponding compensation was made. The result showed that with the increase of weighing quality, the nonlinear error caused by the large deformation increased correspondingly, and the maximum value in the measuring range reached 0.05%. Using the nonlinear error compensation function, this paper eliminated this nonlinear error, and further improved the accuracy of the parallel girder load sensor.