The invention belongs to the field of cellulose modification, and more specifically relates to a cellulose higher fatty acid ester and a preparation method thereof. The weight ratio of cellulose, an esterifying agent and a coreactant, which are the principle raw materials of the cellulose higher fatty acid ester, is 100g:50g-300g:100g-600g. The preparation method comprises steps of pre-reaction and esterification reaction, wherein the esterifying agent and the coreactant are mixed uniformly firstly; the mixture is subjected to pre-reaction for 10 to 30min at a temperature of 50 to 90 DEG C; cellulose is mixed with the mixture uniformly after the pre-reaction, and the mixture is delivered into a ball grinder and is subjected to esterification reaction for 20 to 90min at the temperature of 40 to 90 DEGC with a stirring speed of 100 to 500rmp; and then obtained reaction product is washed and dried so as to obtain the cellulose higher fatty acid ester. Mechanical activation technology is employed so as to increase esterification efficiency of cellulose, shorten reaction time and simplify the processing steps.