To realize spectrum inversion of the nonlinear interference signal in big-angle swing arm interferometer quickly,the principle of a big-angle swing arm interferometer and the influence of the nonlinearity interference signal on the spectrum inversion were analyzed,and then the spectrum inversion based on the non-uniform fast Fourier transform algorithm(NUFFT)was proposed.In this method,the nonlinear interference signal is firstly linearized with the kernel and the convolution algorithm,and then the spectrum inversion of the linearized interference signal is realized by NUFFT.The OPD replace method and the NUFFT algorithm are applied to the spectrum inversion of the nonlinear interference signal.Experimental results show that spectrum inversion precisions of both algorithms are similar,but the NUFFT algorithm is faster in operation.