Abstract The network sampling rate is important in the overhead transmission line monitoring system. A larger sampling rate can provide more available monitored data to be transmitted, which can effectively improve the response speed to emergency events of the overhead transmission line system. Considering the harsh environment of the overhead transmission line wireless network, quality‐of‐service (QoS) requirement becomes an important issue for multi‐hop transmission. Thus, in this paper, an end‐to‐end delay optimisation algorithm for string‐topology multi‐hop wireless network is proposed, by which the maximum packet arrival rate and the allowable maximum sampling rate of network can be obtained with desirable soft QoS guarantees. Based on the IEEE 802.11 standards and the basic probability theorem, a novel end‐to‐end delay performance analytical model is firstly proposed. Then, combined with the derived analytical model, an end‐to‐end delay optimisation algorithm by maximising the packet arrival rate is developed. Finally, a numerical study of a string‐topology multi‐hop network is presented to verify the effects of packet arrival rate, backoff contention window size, hop number, data packet size on the end‐to‐end delay performance.