The invention discloses a roughness detection system and a detection method. The roughness detection system comprises a motion module, a detection module, an industrial control computer, and a pressure sensor module, wherein the motion module comprises a mechanical arm controller and a mechanical arm, and the mechanical arm controller receives an instruction of the industrial control computer through the Ethernet to control the six-degree-of-freedom mechanical arm to move. The invention provides the roughness detection system and the detection method, utilizes the mechanical arm to measure roughness of a blade, can improve the intelligence degree of detection process, can increase detection efficiency, and can perform on-line real-time measurement on workpiece from multiple angles.