Abstract: A prominent M+2H peak in EI spectra is a very rare phenomenon. In the study on the EI behaviour of five quinone-imine dyes, their M+2H peaks were found to be far intense than M peaks. The intensity ratio of M+2H/M obviously increased with evaporation temperature (e. t. ) in EI source. According to the FD data and D_2O, D_2 experiments the above phenomenon seems to be a process of thermal hydrogen transfer, and it is characteristic of the involatile molecule of quinone-imine dyes which are able to bear the large thermal strain and no relation on the ambient conditions such as H_2, H_2O.