In this paper, we develop a time allocation strategy that enhances transmission efficiency of small-size Internet of Mobile Things (IoMT) devices by relaying the information backscattered from user. The system works in a slotted fashion, where each transmission slot is divided into two phases. Specifically, in phase one, user backscatters downlink signals from power beacon (PB) and relay harvests the radio frequency (RF) energy from signal backscattered by user and that transmitted by PB. In phase two, relay forwards the decoded information to destination with harvested RF energy. We formulate the optimization problem and develop an optimal time allocation strategy maximizing throughput considering adaptively adjusted backscattering coefficient and battery capacity constraint at relay. We investigate the effect of transmit power and relay location on the throughput for infinite/finite battery capacity scenario, respectively. Numerical results verify that the proposed time allocation strategy outperforms that with fixed backscattering coefficient.