The behaviour of dielectric constant with the variation of temperature of barium nitrate has been studied between the temperature ranges 35 to 110ºC. In the present measurement it have been observed that the compound has lower value of dielectric constant below 36ºC, which rises upto the maximum value of 14,580 at the moderate temperature of 51ºC. After this temperature the dielectric constant of compound decreases upto the very low value of nearly 8, at the temperature of 108ºC. When the variation of dielectric constant was studied in cooling cycle the peak was observed at 71ºC, above and below this temperature dielectric constant decreases with some intermediate fluctuations. The results have been explained on the basis the crystal structure changes and the possibility of free internal rotation of nitrate group within the crystal lattice at the elevated temperature. The presence of broad peak is explained on he basis of relaxor ferroelectrics, which occurs generally due to heterovalent disorder.