Disclosed in the invention is a three-dimensional single-arm measuring machine with high stability. The three-dimensional single-arm measuring machine comprises a lifting device, a rotating device, a telescoping device, a measuring arm and a support device; the rotating device is fixed at the lifting device; the telescoping device is fixed at the rotating device; and the measuring arm is fixed at the telescoping device. The supporting device includes at least one support rod that is arranged at a motion path of the measuring arm, a spring arranged at the top of the support rod, a support rack connected with the top of the spring, and a support plate fixed at the support rack by a rotating shaft. According to the invention, the measuring machine has the following advantage: the support device is arranged, so that a phenomenon that the measuring arm is bent when being extended due to lack of support can be effectively prevented.