Abstract: The transmission power control algorithm D-FPAV(Distributed Fair Power Adjustment for Vehicular environments) becomes computational expensive when required calculation precision is high, i.e., the step is small. In this paper, a novel transmission power control algorithm SDPC(Steepest Descent Power Control) algorithm is proposed to improve D-FPAV. This algorithm is based on the rapid convergence theory of the steepest descent method. Simulation results show that the effectiveness of SDPC in terms of the number of iterations for computing the transmission power values decreases and converging speed. As a result, the transmission power to transmit their status information can be quickly adaptive to the vehicle dynamic and surroundings situations. Therefore, channel congestion can be effectively controlled and the security of vehicular networks can also be improved.