Abstract: A horizontal polarization antenna for WLAN is illustrated.Firstly the computation equation of bent dipole antenna is derived and the result shows that the change of bent angle can widen the beam width.Then bent dipole antenna together with reflector are analyzed with Moment Method(MM) to realize the directional beam.The shapes of the antenna and the reflector are optimized with Genetic Algorithm(GA) to realize wide beam width,front back ratio(FB) and good VSWR.The method is simple and convenient to realize in engineering.Two examples are illustrated to prove the method efficient.