Hydraulic locking sleeve is a critical part of fiveaxis linkage machine tools, and it elastically deforms under the pressure of oil. Locking of the rotational freedom of the feeding shaft and locking torque are the mayor parameters of hydraulic locking sleeve, which is important for influence precision of the machine tool. Deduced by the nomoment theory and amended by havemoment theory of the thinwalled cylindrical shell, the theoreical calculation formula of locking torque was acquired, and the correctness of the formula was certified by the experiments. The results show that the formula deduced by the nomoment theory and the havemoment theory is suitable for the locking torque calculation of hydraulic locking sleeve.