UDP protocol is the main transmission protocol used in airborne test system for data transmission during flight test. Compared with the TCP protocol, the main feature of UDP protocol is that it is a connectionless oriented protocol, which has low network overhead and fast transmission speed. But the transmission is not reliable, and the data packet may be lost and out of order. Since flight test data processing must take into account the time correlation of data, the flight data processing software needs to develop an appropriate buffer to reorder the data in time. According to the periodicity of network packet time label in flight test, the formula for determining the buffer area size is given, and the rearrangement algorithm of buffer in the case of packet loss and disorder is discussed. Finally, the processing result of real flight test data shows the successful application of the algorithm.