The investigation of (BiTm)3(FeGa)5O12 single crystal films grown by liquid phase epitaxy (LPE) at different temperatures is made by means of X-rays double crystal diffractometry and polarized optical microscopy. The study indicates that the temperature of LPE is very important. With the decrease of temperature, the crystal lattice parameter increases. The crystal film includes two layers of different crystal latticeparameter or orientation. When the crystal lattice misfit ((as-af)/(as)) between the subst-rate and the film is greater than 10-3, the film will crack.