Abstract: Measuring speed,position accuracy and stylus force are three main dynamic characters of digital height measuring instrument (DHMI).Test methods of the three important characters are discussed.And some measuring instruments such as a miniature plane-mirror interferometer and a precise forcemeter are employed for testing these characters.Testing results are presented and the sources and regularity of dynamic errors are analyzed.It is innovative to test and analyze the position accuracy of DHMI.These important test data and conclusions can be utilized to improve the measuring accuracy of DHMI.