Objective To study the key technologies for automatic thickness measurement of soft tissues, and to design the instrument for thickness measurement and verify its feasibility and accuracy by experiments. Methods An experimental system for measuring thickness was designed. The feedback and control of the measurement structure were achieved by the slowing direct-current motor with an encoder. The relationship between master motion and slave motion was built according to the transmission between internal structures. Finally, experiments for thickness measurement were conducted, and, the error size and distribution were analyzed by comparing results of the experiment group with those of the contrast group. Results 27 pairs of thickness data were produced from 9 groups of experiments. The average error was-0. 07 mm and the variance was 0. 03 mm2. There was a small error fluctuation when the data was divided by experiment time, while the error fluctuation was obvious when divided by thickness. Conclusions The instrument for thickness measurement has been shown feasible with a small average error for all data, in spite of the existence of errors.The experiment time, which determines the initial measurement position, has great influence on the result.However, different thickness, which means different opening angle of the instrument, shows negligible effect on the measuring data.