A new method for detecting orthogonal signals of laser interference fringes based on four-quadrant detector is presented. Using the quadrant characteristic of four-quadrant detector and the vector superposition principle of the cosinusoidal interference fringe distribution within the detected region, the orthogonal signals for fringes has been detected successfully. The experimental results show that the orthogonal signals of fringes can be detected expediently by rotating the four-quadrant detector around its center. When the other interference fringes with different period is detected, the orthogonal signals of fringes can also be obtained easily only by rotating the four-quadrant detector to another orientation. In order to restrain noise effectively, a difference technique has been adopted in signal processing. Compared to the traditional detection method, this method is easy to operate and has strong anti-jamming ability.