To achieve desirable plasma density control, supersonic molecular beam injection (SMBI) feedback control system has been developed on EAST tokamak recently. The performance of SMBI is compared with that of gas puffing feedback system. The performance of pulse width mode is better than that of pulse amplitude mode when gas puffing is used for density feedback control. In one-day experiment scenario, the variation of gas input and wall retention can be clarified into two stages. In the first stage the retention ratio is as high as 80%–90%, and the gas input is of about the order of 1022. However, in the second stage, the retention ratio is in a range of 50%–70%. The gas input of a single discharge is small and the net wall retention grows slowly. The result of SMBI feedback control experiment is also analyzed. The shorter delay time of SMBI makes it more quickly to feedback control the plasma density. Result shows that, compared with gas puffing, the gas input of SMBI decreaseds ～ 30% and the wall retention is reduced ～ 40%. This shows SMBI’s advantage for the long pulse high-density discharges in EAST.