Temperature-dependent Raman spectroscopic study on orthophosphates Ba3(PO4)2 and Sr3(PO4)2 were carried out up to 900 ℃. The change of Raman lines and crystal structure has been investigated at high-temperatures. It is found that all the Raman lines exhibit a decrease in frequency shifts and the width of the Raman lines increases with the increase in temperature. The P-O bond lengths in the crystal increase in high- temperature, but the O-P-O bond angles have less change. No phase changes have been observed under 900 ℃.