The main duty of wireless multimedia sensor networks（WMSNs） is to satisfy requirement of network realtime transmission

which is one of the key bottlenecks constraining its development.Present a variable-based exponential windows wireless channel backoff algorithm

aiming at this technical requirement

and the base can be actually adjusted.The channel competition window is adjusted to the minimum to keep high-priority channel access of high-priority multimedia data when wireless channel is clear

the length of a channel competition window of lowpriority data gradually decreases in the form of a power function to keep the low-priority channel access.Experiments show that the sending time interval of high-priority data package is less than that of low-priority data package if the node number of high-priority data package is equal to or less than that of low-priority data package

however

no significant difference exists for network throughput of the two kinds of data package

when the number of nework node is large.