Pr Doped BaTi4O9 gel Was prepared by sol-gel method using Ti (OC4H9) 4, Ba (CH3COO) 2, CH3COOH and CH3OCH2CH2OH as law materials. Through analyzing dry gel thermal treated at different temperatures, the possible synthesis mechanism of Pr doped BaTi4O9 powder was discussed. At first, Ti (OC4H9) 4 hydrolyzes and three dimensional networks form, in which Ba2+ and CH3COO- are mostly in the form of mostly in the form of ions: organic solvent is gradually volatilized through calefaction at 700℃, then the offspring is turned into BaTi5O11. With the temperature increasing to 850℃, BaTi5O11 begins resolving partly and forming BaTi4O9, and at 1000℃ Ba4Ti13O22 forms partly, but BaTi4O9 is the main crystal phase. BaTi5O11 and Ba4Ti13O30 decomposes completely at 1200℃ and forms single-phase BaTi4O9. The infrared (IR) analysis also shows that the absorbing peak of Ti-O bond is not in the characteristic absorption range of Ti-O-Ti (700-900 cm-1) , but slightly shifted to the higher end (908cm) . It is probably because that doping Pr enters into the crystal lattice and Causes the abnormal absorption of Ti-O bond.