Abstract: A new image edge detection algorithm which is based on the theory of fuzzy gradient is proposed in the paper. The steps of the algorithm is as follows: firstly, the original gray image is changed into fuzzy matrix by the normalized tangent function; secondly, gradient matrix of the fuzzy matrix mentioned above is computed; thirdly, the fuzzy gradient matrix which is also called fuzzy set of the gradient matrix is obtained using sine function; and in the end, appropriate threshold which is identified by genetic algorithm based on normalized real-coded is used to segment the fuzzy gradient set into two subsets: the edge point set and non-edge point set. At this point, the image edge points are obtained. To test the speed and accuracy of the algorithm for detecting edge of micro-part image, the experiments have been done taking different kinds of micro-gear as the subjects. The experimental results show that the detecting accuracy is better than 10 μs and the processing time is generally about 1 s. Compared with Canny or Pal-King algorithms, it could be concluded that the performance of proposed new algorithm is the best.