This paper proposes a novel high gain and low sidelobe level (SLL) linear microstrip array antenna for outdoor WLAN applications. The antenna consists of two main parts, which are a linear array and a reflector. The linear array comprises of 10 elements; those have been designed on Rogers RT/Duroid 5870tm with the dimensions of 422×100×10.15 mm3. To gain low SLLs, a series fed network was designed to have the output signals being proportional to the Chebyshev distributions (with preset SLL of -30 dB). Furthermore, Yagi antenna theory has been applied by adding directors above every single element to increase the directivity of the single element. The reflector has been constructed at the back of the proposed structure. Simulation results show that the array can provide high gain of 17.5 dBi and a low SLL of -26 dB. A prototype has been fabricated and measured. Good agreements between simulation and measurement data have been obtained.