The devitrification mechanisms of various $CaO/P_2O_5$ mole ratios calcium phosphate glasses were investigated by non-isothermal DTA technique and by observing the devitrification phenomenon of tested samples after heat treatment procedures. We found that the devitirification mechanism changed from bulk nucleation to sruface nucleation, owing to decreasing the $CaO/P_2O_5$ mole ratio of calcium phosphate glasses. The acrivation energy of devitrification of the fine powder glass decreased with decreasing the $CaO/P_2O_5$ mole ratio of the calcium phosphate glasses also. The major crystalline phase of the resultant products was ${eta}-Ca(PO_3)_2$, the crystalline characteristics was examined by XRD and EDS. We also found the rod-like type ${eta}-Ca(PO_3)_2$ ($5{mu}m$ in diameter and $60{mu}m$ in length) crystal form the micrograph of SEM.