BESIII Collaboration has accumulated the world's largest e+e- collision samples at Ecm = 3.773, 4.009, 4.18 GeV. From analyses of pure leptonic decay D(s)+ -> l+v (l=mu or tau), semileptonic decays of D -> K(pi)l+v (l=e or mu), D+ -> K-pi+e+v, D+ -> omega e+v, D0(+) -> f0(980)e+v, Ds+ -> eta(')e+v, and Ds+ to eta(')e+v, we report the determinations of their absolute branching fractions, CKM matrix elements |Vcs(d)|, the D(s)+ decay constants, the form factors of D semi-leptonic decays. These are important to calibrate the LQCD calculations of decay constants and form factors and to test the CKM unitarity. we have performed an amplitude analysis of D0 -> K-pi+pi+pi-, and have measured the asymetries of D+ -> K_S/LK+(pi0) and D0 -> K_S/Lpi0(pi0), as well as the branching fractions for D0(+) -> PP and some decays containing two KSs. In addition, we also measure the branching fractions for Ds+ -> omega pi+, omega K+ and bayon decay of pn.