Abstract: Femtosecond time-resolved mass spectrometry is the combination of femtosecond pump-probe technique and flight time mass spectrometry. By the technology, ion mass spectra from ionization or dissociation of the molecules excited state can be measured under different pump-probe time delays. The temporal information of the population of the excited states varies with the change of the strength of mass spectra. Some information is given, such as:the accurate lifetime of the excited state and Rydberg state, coupling information of potential energy surface and non adiabatic of molecular excited state, and excessive state information. The application of femtosecond time-resolved mass spectrometry in ultrafast dynamics process is introduced, such as:recent advances of molecular excited states and the latest progress of Rydberg state for dissociation, isomerization, conversion, and system cross. And it is pointed out that femtosecond time-resolved mass spectrometry will play an important role in the study of some new phenomena.