A facile and controllable ethanol/water aided hydrothermal process was developed to prepare the NaCaSiO3OH:Tb3+/Eu3+ phosphor. The morphologies were in situ constructed with the phase transformation from NaCaSiO3OH to Na2Ca2Si2O7, and the intrinsic crystal structural transformation mechanism and the dependence of their photoluminescence tuning on the Tb3+/Eu3+ ratio have been discussed.