The invention discloses a processing method of hard bean curd. The processing method comprises the following steps: 1, raw materials and auxiliary materials are prepared, specifically, soybean raw materials and magnesium chloride auxiliary materials for implementing production license management are prepared; 2, soybeans are soaked, specifically, soybean raw materials are taken and cleaned with normal-temperature water, and then the cleaned soybean raw materials are soaked for 8 h-14 h; 3, grinding is conducted, specifically, the soaked soybean raw materials are drained, transferred to grinding equipment and ground to obtain soybean paste; 4, separation is conducted, specifically, the soybean paste is taken and subjected to centrifugal filtration through centrifugal equipment to obtain a semi-finished product; 5, boiling is conducted, specifically, the semi-finished product is taken and boiled for 5 min-6 min in a 104 DEG C-108 DEG C temperature environment to obtain soybean milk; 6, burdening is conducted, specifically, magnesium chloride auxiliary materials accounting for 0.29-0.31 wt% of the soybean raw materials are weighed for later use; and 7, marinating is conducted, specifically, the soybean milk is transferred into marinating equipment, the weighed magnesium chloride auxiliary materials are dissolved into water according to a mass ratio of 1:5, the obtained solution isadded into the soybean milk, and marinating is conducted for 18 min-22 min so as to obtain the hard bean curd. The production efficiency is high, the yield is stable, and raw material waste can be effectively avoided.