Introduction of cyano group into the molecules of borane-based hypergolic fuels can greatly reinforce the hydrolytic stability. By the formation of complex between BH2CN and imidazole, six complexes were readily prepared from N-alkyl substituted imidazole hydrochloride salts and NaBH3CN in THF and fully characterized by H-1 and (CNMR)-C-13, IR spectroscopy, high-resolution mass spectrum, and differential scanning calorimetry (DSC). Among them, 1-allylimidazole-cyanoborane complex (5) displayed some attractive properties such as water immiscibility and good hydrolytic stability, high density (> 1.0 g cm(-3)), good thermal stability (T-d, 193 degrees C, onset), high calculated density impulse (I-sp, 358s g cm(-3)), ultra-short ignition delay time (WFNA, 3 ms), and super low viscosity (8.4 mPa s), showing the real application potential as a fuel and an efficient fuel additive in bipropellants.