The vibration signal generated by combustion in diesel engine can be converted from one-dimensional time domain signal to a two-dimensional time-frequency domain using S-transform and time-frequency domain, which contains richer information of combustion status. A FIR band-pass filter was designed according to the frequency range of the time-frequency domain. The vibration signals generated by combustion in different combustion statuses were passed through the band-pass filter and the filtered signal had well relation with combustion status. A sample bank could be built using the filtered signals. The similar degree between the measured signal and the templates were calculated and the combustion status of the diesel engine was estimated according to the peak magnitude of similar degree. Finally, the simulated results show that the method is feasible.  