Aim to the low measuring precision of non-cylinder pin hole using the coordinate measuring machine(CMM)and pneumatic measuring instrument, a new solution is proposed which use the high-precision digital lever probe to detect the contours of pin hole with a single clamping situation. The measuring principal of non-cylinder pin hole of piston is introduced and the functions and measuring processes of the measurement system are also presented. The software modules are given and the probe centering error and the parallelism movement error are discussed detailedly. A measuring example is given in the end. The measuring results show that the measurement system has the ability to detect the contours of pin hole with high-precision and efficiently.