Considering an offshore oilfield was a sandstone reservoir and its completion had characteristic of gravel pack, this paper studied the acidification plug pre-removal system. After the determination of type and concentration of acid, screening of additives and physical simulation experiment, acidification plug pre-removal system was determined. Ahead acid and overflush acid were preliminarily confirmed as hydrochloric acid with mass fraction of 7%. The formula of primary acid was preliminarily established: 5% hydrochloric acid, 5% fluoboric acid, 1% acetic acid. The corrosion rate to stabilized na-bentonite of ahead acid and overflush acid was only 2.78% and that of the primary acid was up to 21.77%, while the corrosion rate to gravel of that was 0.38% and 1.04%, respectively. The optimum dosage of corrosion inhibitor BJ was 0.5% and the rate of corrosion inhibition was more than 95%. While the optimum dosage of clay stabilizer WS-1 was 3% and the rate of anti-swelling was 85.96%. The best formula of acidification plug pre-removal system was obtained as follows: ahead acid and overflush acid consisting of 7% hydrochloric acid, 0.5% BJ and 3% WS-1, main acid consisting of 5% fluoboric acid, 5% hydrochloric acid, 1% acetic acid, 0.5% BJ and 3% WS-1. The system had good compatibility. The effect of plug removal was satisfying while the permeability recovery ratio was improved more than 7 times. The acid fluid system could dissolve the flocculation, produce larger pores, and improve the permeability to achieve the purpose of plug removal.