The invention provides an acidic plug removal agent for sulfate scale of an immovable string of an oil-water well. The acidic plug removal agent is prepared from the following raw materials by weight percent: 10-20% of multi-element organic acid liquor, 20-25% of acetic acid compound, 5-10% of an organic phosphine compound, 5-10% of a reducing agent, 3-5% of an activating agent, 1-2% of a wetting agent, 1-2% of a dispersing agent and the balance of running water. The invention mainly aims to solve the problem that the conventional acidic plug removal cannot remove the plugging sulfate scale and to promote the effect of acidic plug removal for oil-water well; the alkali sensitive damage to the reservoir caused by an alkali sulfate scale plug-removing solution can be avoided; the reservoir is protected; the multi-section plugging injection construction is reduced; the construction process is simplified; the low corrosion thereof is utilized to realize the plug removal of the immovable string; the operation cost is lowered.