We explore the CP violation in the charged Higgs production associated with a top quark at the LHC in the minimal supersymmetric standard model. The supersymmetric phases of gaugino masses and trilinear A terms lead to a CP violation of the cross section in the pp-->gb-->tH(+/-) process through loop corrections to the tbH(+/-) vertex. We find that more than 10% of CP violating asymmetry is possible when the charged Higgs boson is heavy enough.