In this paper, we propose an assignment algorithm of time slots for wireless links in IEEE 802.16 multi-hop relay networks. The main purpose is to reduce transmission latency between user stations and base stations as well as maintaining total network throughput. The proposed algorithm is based on the existing method, which aims better network throughput and guarantees certain frame length, but changes the order of time slot assignment without network throughput changed to decrease the transmission latency. It also accommodates the weighted time slot assignment, which is consistent with IEEE 802.16j specifications. Performance evaluation is conducted through both of simulation experiments and numerical calculations and confirm that the proposed algorithm can decrease the transmission latency by up to 15% on average compared with the existing random assignment algorithm, and can provide an time slot assignment with smaller transmission latency in shorter calculation time.