The invention discloses a variable concentration carbon dioxide acid fracturing method. The variable concentration carbon dioxide acid fracturing method comprises the following steps that (1), an acidtank A, an acid tank B and a water tank A are directly connected with one end of a fracturing blender truck A; (2), the other end of the fracturing blender truck A is connected with a fracturing truck A and a high pressure manifold A in series in sequence; (3) a water tank B, a fracturing blender truck B and a fracturing truck B are connected in series in sequence and then is connected with the high pressure manifold A, and then the high pressure manifold A is connected with a wellhead; (4) a CO2 tank car, a CO2 pump truck, a fracturing truck C and a high pressure manifold B are connected inseries in sequence and then are connected with the wellhead; and (5) when acid fracturing construction is carried out, the total pump liquid injecting volume and the total pump injecting displacementof the fracturing truck A are VA and QA respectively, the total pump liquid injecting volume and the total pump injecting displacement of the fracturing truck B are VB and QB respectively, and the total pump injecting carbon dioxide liquid volume and the total pump injecting carbon dioxide displacement of the fracturing truck C are V2 and Q2 respectively. According to the variable concentration carbon dioxide acid fracturing method, the acid liquid concentration and the carbon dioxide concentration are controlled and changed stage by stage, the fracture conductivity is enlarged, and the acid fracturing effect is remarkably improved.