Hi Lavanaya,
Back fat reduction takes time to lose. Regular exercises and proper amount of healthy diet play an important role to reduce your back fat. Fat burning depends on whether your body fat percentage is high or normal. If your body fat percentage is in normal range then its better that you do more of weight training exercises like Lat pull down, rowing, shalabhasana, etc along with alternate days of cardio training exercises. And if your body fat percentage is high then its better that you do more of cardio training exercises like jogging, running, brisk walking, skipping,etc. You need to do these exercises atleast for 45 min in a day for better results.