The invention provides a design method of a D-dot electric field sensor of a power transmission line. The design method includes steps: S1, obtaining parameters of the power transmission line, establishing a power transmission line electric field distribution model, and obtaining the distribution condition of surrounding electric fields of the power transmission line; S2, obtaining design parameters of the design target D-dot electric field sensor, establishing an electric field sensor model, and introducing the electric field sensor model into the power transmission line electric field distribution model; S3, establishing a field-circuit coupling model and an equivalent circuit of the design target D-dot electric field sensor and the power transmission line, performing simulation analysis and calculation on a transfer function of the field-circuit coupling equivalent circuit, and obtaining output parameters of the design target D-dot electric field sensor; and S4, determining the error between an output result of the design target D-dot electric field sensor and a theoretical calculation output result, wherein the current electric field sensor model satisfies the design requirement if the error is within a design range; and performing optimization adjustment on the design parameters and returning to S2 if the error is out of the design range. According to the method, the design precision and the product progress are improved, and the cost is reduced.