The collinear interaction between incident linearly chirped Gaussian pulses and single-frequency continuous microwave magneto-static surface waves (MSSW) in a horizontally magneto-optical film waveguide is studied and the coupling equations between optical pulses and MSSWs are presented, which can be used to analyze MSSW-based optical pulse signal processing. The diffraction characteristics of incident linearly chirped Gaussian pulses at 1310 nm and 1550 nm wavelength are in detail analyzed by the analytical and numerical methods respectively, and the same results are obtained. It is shown that, the full width at half maximum (FWHM) of diffracted optical pulses can be reduced by using a larger slope of phase-mismatching distribution or an incident optical pulse with large chirp parameter. The diffracted optical pulse corresponding to the 1310 nm carrier has a larger peak intensity, while the 1550 nm optical pulse is much more easily compressed for the case considered here. The influence of magnetic loss on output pulse intensity and pulse width is analyzed. For an ordinary magneto-optic (MO) film, the pulse compression effect is not basically affected by magnetic loss.