这个是有些困难的。您可以查看下说明：
The maximum payload size for an application is based on several factors. The MAC layer provides a constant payload length of 116 (can be changed in f8wConfig.cfg – MAC_MAX_FRAME_SIZE). The NWK layer requires a fixed header size, one size with security and one without security. The APS layer has a required, but variable,header size based on a variety of settings, including the ZigBee Protocol Version, APS frame control settings, etc.
Ultimately, the user does not have to calculate the maximum payload size using the aforementioned factors. The AF module provides an API that allows the user to query the stack for the maximum payload size, or the maximum transport unit (MTU). The user can call the function, “afDataReqMTU” (see “af.h”) which will return the MTU, or maximum payload size.