The invention provides a preparation method for reducing mechanical sensitivity of HMX. The preparation method comprises the following steps of: preparing an alkali solution with a pH value being 8-11; dissolving catechol substances into the alkali solution to obtain a catechol alkali solution with concentration being 0.1g/L-20g/L, wherein the pH value of the completely dissolved solution is greater than 7; putting HMX into the catechol alkali solution and stirring for 0.1-24 hours to obtain a mixed dispersion liquid; carrying out suction filtration cleaning on the mixed dispersion liquid treated in the step III, and cleaning the mixed dispersion liquid by distilled water; drying the mixed dispersion liquid for 1-24 hours at a temperature of 50-80 DEG C to obtain an modified HMX material. The preparation method is simple in process, and physical characteristics such as crystal shape, density and the like of the HMX are not changed; and the modified HMX material has relatively low mechanical sensitivity, so that the friction sensitivity can be reduced by 30%, characteristic height is improved by more than one time, and therefore, the HMX has relatively high safety performance.