Fiber optic gyro curve mode detection system is a method for measuring the pavement curve mode. By combining the detection principle of fiber optic gyro and the pavement evenness index, a method for obtaining pavement evenness is proposed. The experimental analysis and application results show that the probability distribution and standard deviation of the angular velocity collected by FOG in the process of curve measurement have a strong relevance with the pavement evenness. By extracting the bridge curve height standard deviation detected by FOG, the pavement evenness coefficient can be obtained. This method can reflect the macro evenness of the pavement surface and the driving comfort transferred from the pavement to the vehicle. It also can realize the simultaneous measurement of the bridge curve and evenness, which presents the advantages of convenient, efficient and accurate, and great application and promotion value.