The invention discloses a method for identifying axle load of a single vehicle based on bridge dynamic strain, wherein the method belongs to the field of bridge testing, health monitoring and overload vehicle control. A high-resolution strain testing device (sensor) is configured in a beam type bridge span or a maximal strain reaction cross section. A bridge dynamic strain time travel curve under the function of the vehicle is tested. Filtering noise-reduction or fitting is performed on the dynamic strain time travel curve. Furthermore one-order and two-order derivations are performed. According to a definite-element simulating result, a curve derivation result and vehicle driving speed, the axle load of the vehicle is calculated. According to the method of the invention, configuration of only one strain testing cross section on the bridge is required, thereby realizing simple mounting and low cost. Damage of a bridge surface structure or a pavement structure is not required, and no damage to an existing bridge load is realized. Furthermore simple recognition algorithm and high accuracy are realized.