The invention discloses a calculation method for the mixing amount of a clay inhibitor in concrete. The calculation method comprises the following steps: 1), an MBS (methylene blue of sand) value of sand and an MBG (methylene blue of gravel) value of gravel used for batching concrete are measured; 2), the total amount sigma MB of aggregate of the concrete per cubic meter is calculated; 3), the total amount of exchangeable cations in the clay of the concrete per cubic meter is calculated according to the total MB amount of the aggregate; and 4), mixing mass of the clay inhibitor into the concrete per cubic meter is calculated according to the total MB amount of the aggregate or the total amount of exchangeable cations in the clay. Compared with the conventional method that the mixing amount of the clay inhibitor is calculated according to the total amount of a cementing material in the concrete per cubic meter, the calculation process is simple and convenient, the mixing amount changes with mineral species and different content of the clay in the aggregate, so that practical conditions of different aggregate can be met effectively, mixing effects can be predicted according to the species and different mixing content of the mixed clay inhibitor, and application of the clay inhibitor can be better guided.