Due to the limitation of diffraction limit, the conventional optical microcopes are unable to obtain resolution of nanometer scale. In order to break through the diffraction limit, a new method of microscopic imaging based on random pulse coding and time-sharing multiplexing is presented. It can code and decode the indistinct image the of point spread function efficiently, and reconstruct the original image. The mathematical principle of the proposed method is expounded, and the simulation analysis in the different sparseness of coding and different image frames is carried on. The results show that the super-resolution image of the tested sample is obtained using the sparse coding and about 1000 frames image. The proposed method can break through the diffraction limit, and it is effective and suitable for the study of living cells.