Synchronous medium access control（ MAC） protocols based on cross-layer competition for wireless sensor networks（ WSNs） enable multi-hop transmission of multiple data packets in a cycle. Traditional protocols transmit both the request-to-send data（ RTSD） process and the conrm-to-send data（ CTSD） process in the same data transmission scheduling window（ i. e. data window）

this reduces the length of the multi-hop flow setup in the data window. In a multi-hop scenario

this degrades both the packet delivery ratio and the end-to-end transmission delay. Therefore

a new cross-layer competition based synchronous MAC（ CLC-MAC） protocol is proposed. The proposed protocol uses a novel cycle structure

which contains two separate windows for transmitting data request and confirmation packets. It accommodates the request-to-send data process in the data window and the conrmation-to-send data process in the sleep window. Simulation results show that proposed protocol outperforms pioneer routing frame MAC（ PRMAC） both in terms of the end-to-end delay and the packet delivery ratio.