Ethyl orthosilicate, barium acetate, and calcium acetate were used as raw materials, and the three were evenly mixed through a liquid phase miscible method; to obtain pretreatment powder, and then the interaction of various substances of the pretreatment powder in the solid phase synthesis process were studied by XRD and DTA-TG. At the same time, the effects of different heating rates, different calcination processes and holding time on the synthesis of high expansion coefficient Ba1.55Ca0.45SiO4 were explored by XRD. The results show that during the solid phase reaction, the acetate in the pretreated powder first decomposes to form the corresponding carbonate, and at the same time, the corresponding BaCa(CO3)2 solid solution may be formed. The melting point of carbonate begins to decompose. When the temperature rises to 1 063 ℃, BaCO3 reacts with SiO2 to form Ba2SiO4 crystals. When the temperature continues rise to 1 144 ℃, Ca2+solid solution enters Ba2SiO4 crystals to form Ba1.55Ca0.45SiO4 crystals. In addition, when the pre-processed powder is calcined or pressed into a strip sample for heating, it is difficult for BaCO3 in the powder to fully participate in the reaction, and when the powder naturally accumulates, it is heated to 1 250 ℃ at a heating rate of 1 ℃/min after 5 h, Ba1.55Ca0.45SiO4 crystals with an average thermal expansion coefficient of 12.63×10-6 K-1 were obtained.