Heavy quarks are almost initially produced and the number is conserved during the evolution of the hot medium produced in Heavy Ion collisions. We firstly take into account the charm conservation effect on charm hadron hadronization via sequential coalescence model. In the frame of sequential coalescence, the charm conservation enhances the earlier hadron production and suppresses the later production. This relative enhancement (suppression) changes significantly the charmed hadron ratios in heavy ion collisions at RHIC and LHC.