Abstract: In This paper, a new measuring method for selecting the adjusting spacer of truck's rear axle gear by measuring the dimension of the installing space of truck's rear axle gear is presented. Based on the measuring method, the measuring machine for installing station of truck's rear axle gear has been designed and manufactured. This machine is very simple to operate and the measuring result can be given immediately. Furthmore, the measuring precision is very high.the machine has been successfully used in truck assembly line. Due to using the machine, the quality and work efficiency are raised noticeably.