The gravel fill sand control technology of viscosity steady acidizing fluid was researched in view of the problem that the conventional acid treating had easily caused reservoir sand production and immediate vicinity of wellbore blocking. The formula of the NWS-Ⅰacidizing fluid system was obtained as follows: 6% HCl, 3% ZNW, 0.1% HPAM, 0.05% aluminium citrate (YL-1), 1% ammonium chloride, 1% ion stabilizers, 1% XP inhibiter, 0.5% CF-5B cleanup additive. After the core was treated by viscosity steady acidizing fluid, the dissolution rate of core decreased from 1.58% to 0.55%. The exit pH value was about 4.7, and the effective distance was more than 2.0 m. The subsidence time of gravel in viscosity steady acidizing fluid was longer than 10 min. The sand mixed uniformly, subsidence velocity was homogeneous. The retention rate of viscosity was up to 83.3%, 68.7% and 59.7% respectively, when the acidizing fluid was sheared at 30, 60 and 80℃ with 120 min, which had a good rheological behavior. When the concentration of acidizing fluid increased from 200 to 1000 mg/L, the damage rate of core increased from 0.6 to 1.27, which had little damage to formation. Compared with mud acid, viscosity steady acidizing system could restrain second sediment better. Field test in Shengli oilfield indicated that the productivity of five test wells increased 1.54times, construction success rate was 100% and valid period was long.