Abstract: In order to obtain high-quality KMgF3 crystal,it was grown by Czochralski method in the CF4 atmosphere.The volatiles and remainders of the crystal growth were analyzed,and the infrared transmission spectrum of the crystals was measured.The main volatile matter is KF,and there is MgF2 phase in the remainders while crystallization rate is high.In the infrared transmission spectrum there is no OH- absorption,but COH absorption is obvious.Above results display that CF4 atmosphere is favorable for eliminating oxygen source of the growth atmosphere,such as H20 etc.To get high quality KMgF3 crystal,it is not negligible to inhibit the volatility of KF effectively and to replenish KF suitably in the crystal growth.