Acidizing radius design is an important determinative factor for the economic benefit of acidizing. According to theoretical derivation on Darcy’s formula, the theoretical models of stimulation ratio and optimum acidizing radius for conventional injection well and fractured injection well are obtained. With the example of Hailaer Oilfield, the optimum acidizing radius of different types wells is obtained. This design model is applied for 7 wells in Xinanling Group of Hailaer Oilfield. The results of field tests indicate the design model is practical and can also be used to guide the acidizing design for other sandstone reservoirs.