1, 1-Diamino-2, 2-dinitroethylene (FOX-7) was prepared from acetamidine hydrochloride and malonate by condensation, nitration and hydrolysis. The structure of FOX-7 was characterized by IR, MS, NMR. Organic solvents was added in the nitration process, the reaction conditions were optimized as t=3 h, n_H2SO4:n_{4, 6-dihydroxy-2-methylpyrimidine}=9:1, T=10 ℃, V_{organic solvents}:V_H2SO4=1:1, the yield of FOX-7 is 89.6%.