The invention belongs to the field of automatic detection, particularly relates to an on-line measuring method for the radials profile of a compressor disc-like part of an engine. The method comprises the following steps that the measuring path of a measuring head is planned; the radius of sphere of the measuring head is corrected; characteristic points on the profile of a compressor disc are selected as measuring points; the motion program of the measuring head is edited; the motion track of the measuring head is optimized in virtual simulation software; the motion program of the measuring head is run; the measuring head traverses all the measuring points; the mean value of the measured values of the measuring points after errors are compensated is compared with the design theoretical value of the compressor disc part; when the measured values are within the design tolerance zone scope of the part, the processing size of the measured compressor disc part is considered to be qualified; otherwise, the processing and measurement are carried out again, until the size of the part is qualified. According to the method, a traditional manufacturing mode in the current industry that a design characteristic is matched with a set of measuring tooling is changed, so that the tooling manufacturing cost and the rework hours are saved, the one-time qualified rate of product processing is improved, the new product development cycle is shortened and the production cost is reduced.