For the existing Unmanned Aerial Vehicle Ad-Hoc Network (UANET)media access control protocol Statistical Priority-based Multiple Access Protocol (SPMA), the full-load threshold calculation process has slow convergence, and the full-load threshold cannot be adaptively changed with the channel carrying capacity. This paper proposes a low-delay UANET threshold adaptive access protocol. The full-load threshold fast convergence mechanism shortens the threshold calculation time after the system is turned on, reduces the transmission delay of the accumulated data in the initial stage, and adopts the full-load threshold adaptive adjustment mechanism. Therefore, the system can be adapted when the external channel environment changes. The full-load threshold of the channel is adjusted, and the channel carrying capacity can match the actual transmission. When the external channel environment changes, the channel’s full load threshold is adaptively adjusted to match the channel load capacity with the actual channel load. When the channel load capacity is reduced, the data can be adjusted to increase the data transmission success rate while maintaining constant throughput with reduced data transmission delay. The simulation results show that the performance of the protocol in the UANET is better than that of the existing UANET SPMA protocol.