Employing multiple UAVs as a swarm for investigation and surveillance can complete more complex missions. Since novel sensors equipped, vast amounts of data are continually generated as the increasing number of UAVs. Therefore, the process of multi-source data and the valuable information from the multi-source data is of significant importance. These data formats vary from traditional data to dynamic data with the characteristic of multi-source. Considering that vast amounts of multi-source data from UAV swarm require higher throughput performance of transmission schemes, complex field network coding (CFNC) is selected for UAV cooperative system. However, adverse effects like inter-user interference of fading channels will limit the reliability performance of UAV cooperative system. To improve the reliability performance and recover more accurate valuable information, we propose a precoding-based CFNC strategy for multi-source UAV cooperative system. The proposed transmission scheme processes data through precoding matrix, which is obtained by the transformation of channel state matrix. Compared to conventional CFNC schemes, precoding-based CFNC scheme improves the accuracy of detections. Through theoretical analysis and experimental results, the precoding-based CFNC transmission scheme not only maintains high throughput, but also recover more valuable information and achieves better reliability performance.