Abstract: When the energy of the range-spread target return is not equable in all range cells, a robust detection method for range-spread target is proposed. The proposed detector is a modified generalized likelihood ratio test based on order statistics (OS-GLRT). The modified OS-GLRT adopts “the rule of OR” and fuses the decision results of the OS-GLRT detectors with all the assumptions about the number of valid range cells to make a final decision. The resulting modified OS-GLRT doesn’t need apriority information about the number of valid range cells, and can overcome the sensitivity of OS-GLRT detector to the number of valid range cells. It shows that the modified OS-GLRT is a constant false alarm rate (CFAR) detector. The performance assessment conducted by Monte Carlo simulation confirms the effectiveness and robustness of the proposed detector. As the modified OS-GLRT detector does not need to estimate the number of valid range cells, it is easy to work in practice.