The invention discloses a detection method for detecting metal flatness by multi-point matrix type eddy current sensors. According to the method, the sensors are firstly calibrated by using a multi-line chart; the sensors are mounted on an inspection tool; the mounting heights of the sensors are calibrated; the sensors are calibrated on a plane position on a to-be-detected workpiece by using a plane coordinate; the measured value of each sensor to the plane of the to-be-detected workpiece, actual distance values obtained through conversion and mounting height errors are formed into a spatial coordinate of each detection point; and a flatness deviation value of a measured surface is calculated by adoption of a multi-point least squares method. The detection method provided by the inventionhas the advantages of being high in detection precision, short in detection time, small in undulation angles of the eddy current sensors, and free of contact with the workpieces for measurement, can be applied to the surface flatness detection of various metal planes, and is suitable for the metal planes which have high reflectivity or cannot be contacted when the traditional mechanical contact measurement or laser displacement sensor measurement cannot be used.