The invention discloses a Rhizoma Trichosanthis starch preparation method. The method includes steps: (1) cleaning; (2) grinding including primary comminuting and secondary comminuting, wherein alkekengi 2-4 times of weight of Rhizoma Trichosanthis is added during secondary comminuting to obtain Rhizoma Trichosanthis paste; (3) screening; (4) washing and concentrating; (5) fermenting, to be more specific, adding 30-40DEG C water 0.5-0.7 time of weight of washed starch milk into the washed starch milk, and fermenting for 10-15h; (6) dewatering; (7) drying, to be more specific, adopting an air flow drier for drying at a temperature of 40-50 DEG C until starch powder being 20-25% in moisture is obtained; (8) cooling; (9) screening and packaging. The Rhizoma Trichosanthis starch prepared according to the Rhizoma Trichosanthis starch preparation method has advantages of good color, high viscosity and high safety and quality.