The temporal response of a Fabry-Perot etalon filter to the short optical pulses has been studied.It is found that due to the interference between the multi-reflected beams inside the etalon,the transmitting pulse is composed of a series of sub-pulses which are separated by the one-way traverse time of the light inside the etalon.Under certain circumstances,the sub-pulses merge together resulting in a broadened output pulse,and the time difference between the peaks of the output and input pulses may not be equal to the one-way traverse time. Studies have also been carried out for the chirped pulse and dispersion etalon, which led to the expressions of the transmitting sub-pulses.