A transmitting array design scheme for ground microwave wireless power transmission system is presented. To reduce the cost and simultaneously ensure a high transmission efficiency, a microstrip array based on subarrays technique is proposed. And the stepped amplitude distribution is adopted. The feeding network with the substrate integrated coaxial line technique is designed. With this structure, good isolation can be guaranteed. For the ground demonstration system associated the space solar power satellite, diameters of the transmitting and rectenna arrays are 1.6m and 7m, respectively. And they are separated by 100m. A high beam collection efficiency of 92.25% is achieved.