The invention discloses a pure electric automobile front cabin resistance reduction device and a work method thereof, and belongs to the field of pure electric automobile resistance reduction. A ventilation passage of the resistance reduction device is arranged in a front cabin of an automobile; an outlet and an inlet of the ventilation passage are respectively provided with a grille sheet; the grille sheets are connected with a step motor; a temperature sensor, a humidity sensor and the step motor are connected with a controller through conducting wires; the controller judges the work mode of the resistance reduction device according to the received temperature, humidity and automobile speed; when the automobile speed is higher than 60km/h and the weather condition is good, the resistance reduction device starts to work; the controller sends rotating corner signals to the step motor; the step motor drives the grille sheets to rotate for different angles; the rotating angles are gradually increased along with the automobile speed acceleration. On the basis of different running automobile speeds of the automobile and different weather conditions, the grille sheets rotate for different angles, air flow entering the front cabin is guided to the bottom of the automobile, the aerodynamic resistance of the whole automobile is reduced; meanwhile, the aerodynamic lift is reduced; the automobile operation performance is improved; the traveling distance of the pure electric automobile is improved.