The present work concerns the evaluation of emitting multiwall carbon nanotube (MWCNT) temperature, here referred to as "emission point" temperature. The latter is related to the onset of thermal degradation of polymer molecules neighboring to the MWCNT. The investigation method combines the registration of both current voltage characteristics and thermal degradation volatile products for "polymer-MWCNT" composite emitter during the emitting process. Our experimental setup involves a time-of-flight mass spectrometer and field emission unit.