Gear design is one of the most critical components in the Mechanical Power Transmission industry. Among all the gear design parameters pressure angle is the most critical parameter, which mainly affects the load carrying capacity of the gear. Generally gears are designed with a symmetric pressure angle for drive and coast side. It means that both flank side of gear are able to have same load carrying capacity. In some applications, such as in wind turbines, the gears experience only uni-directional loading. In such cases, the geometry of the drive side need not be symmetric to the coast side. This allows for the design of gears with asymmetric teeth. Therefore new gear designs are needed because of the increasing performance requirements, such as high load capacity, high endurance, long life, and high speed. These gears provide flexibility to designers due to their non-standard design. If they are correctly designed, they can make important contributions to the improvement of designs in aerospace industry, automobile industry, and wind turbine industry.In this paper we present a mathematical model of helical gear pair with an asymmetric pressure angle. We have increased the pressure angle of gear on the drive side to increase the load capacity and performance of the gear pair in terms of noise and mesh stiffness while transmitting power. Also we have analyzed the results of bending and contact stresses generated on gear pair with the asymmetric pressure angle.