Microarray is a widely used method in molecular biology. The essential problems of microarray image analysis are to locate spots and quantify the intensity of each spots. Because of the rapid progress in gene technology, fully automated microarray image analysis is required to process thousands upon thousands images produced in hybridization experiments. In this paper we address an efficient and fttlly automated method to solve this problem. The only precondition of our method is that the spots are arrayed in a grid. An implemented program based on our method can cope with the following problems: global rotation of the grid, absence of grid spots, and local deviation of the spot from its specified grid position. In grid fitting step, we imported a method introduced in document layout analysis system to estimate the rotation angle and the grid unit size, spots location amplification is then performed to locate all the grid elements. And in quantification, we use the local threshold method to make the simplest integration method getting a reliable result. All algorithms used in the program can efficiently run without operator' s intervention.