Timeslot assignment algorithm is one of the important technologies on ground-to-air data link in improving the communication efficiency of the system. In accordance with the characteristics of ground-to-air data link, the paper proposes a new algorithm---algorithm of bintree average allocation in the Block---to enhance validity of timeslot assigning of the moving users. The algorithm makes the management model more convenient, the uniformity of time interval better, and the denotation of the timeslot easier.