Optical imaging degradation is one of the most important factors for image quality in digital optical microscopic imaging. Combined with the digital microscopic imaging system and optical objective lens measurement, a fast gradient constrained restoration method is proposed based on point spread function estimation under different fields. By measuring the modulation transfer function of objective lens, the point spread function is obtained with different fields. A novel restoration approach is designed with the L0 gradient constraint as a regularized term. Meanwhile, the weight image stitching method is designed for the restoration of multiple fields. The image data with different objective lens are tested, and the evaluation methods are used for assessing the results. The results show that the gradient constrained microscopic imaging quality improvement method with the objective lens measurement is suitable for microscopic imaging system for its good restored effect and high computational efficiency, it takes only 1.62 s for the image size of 2048 pixel×1536 pixel.