This paper proposes a new MAC protocol applied for a new kind of data collection applications that use a wireless sensor network employed with one unmanned aerial vehicle (WSN-UAV). In this protocol, the sensors are classified in different groups based on priorities and communicate with the UAV by a CDMA-based transmission scheme. The Prioritized Frame Selection based CDMA MAC protocol (PFSC-MAC1) incorporates not only the value, but also the variation trend of the receiving power of the beacon signals. This protocol provides a low rate of failed packet due to the mobility of the UAV, which is the most critical metric in these types of applications. In addition, an optimal number of priority groups have also been introduced to guarantee a minimal transmission interval and a lowest failed packet ratio. Numerical results have also shown the efficient energy compared with the other protocol that is based on TDMA. This protocol is simple but promising for various applications that collect data from a large area sensor network.