介绍了一种以光纤作为传感器的表面粗糙度在线测量系统。提出了用镜反射光强与３０°方向散射光强的比值获取表面粗糙度的方法，测量范围大，而且测量结果不受光源和工件材料的影响，测量精度高。并针对磨削过程中测量存在的问题，提出了采用冷却液冲排铁屑和被污染的冷却液的解决方法。该系统对磨削过程进行了实际测量，得到与实际相符的结果。 An on-line surface roughness measuring system based on optical fiber is introduced. The method of obtaining the surface roughness by the ratio of the light intensity reflected by the mirror and the light intensity scattered in the direction of 30 ° is proposed. The measurement range is large, and the measurement result is not affected by the light source and the workpiece material, and the measurement accuracy is high. In the light of the problems existing in the process of grinding, a solution to the problem of using chilled iron to polish scrap iron and contaminated coolant is proposed. The system actually measured the grinding process and got the exact result.