We calculate the full one-loop electroweak (FEW) corrections to $H^-\to\widetilde��^-_1\widetilde��^0_i$ in the minimal supersymmetric standard model (MSSM), and compare with the leading order (LO) corrections including the loops of the (s)quarks only in the third generation and the complete leading order (CLO) corrections including the loops of the (s)quarks in all the three generations. We find that the magnitudes of the FEW corrections can be larger than 10% for $\tan��>30$. Moreover, comparing with the FEW corrections, both of the LO and the CLO corrections are negligible small for the mode 1($H^-\to\widetilde��^-_1\widetilde��^0_1$) when $\tan��<5$, and for the mode 2($H^-\to\widetilde��^-_1\widetilde��^0_2$) when $\tan��>45$, respectively, since there are not enhancements from the Yukawa couplings. We also calculate the FEW corrections in the minimal supergravity (mSUGRA) scenario, where the FEW corrections can be larger than the LO and the CLO corrections by more than 60% and 50%, respectively.

38 pages, 18 figures, revised version, to appear in Phys. Rev. D