Abstract: The InSight mission is a great milestone in the history of Mars' seismic exploration after the Viking 2 lander. We first review the scientific goals of the InSight mission and its seismic observation experiment on Mars' surface. We then present the discoveries in the InSight seismic data. Both the pressure-induced ground deformation and the HP³ self-hammering signals were detected by the InSight seismic instrument. These data are further used to constrain the physical properties of the surface regolith and the inversion of the underground structure at the InSight landing site. Besides, the structural resonance around 2.4 Hz allows us to distinguish the natural response from the mechanical vibration such as the lander mode. Non-seismic noise like the glitches and donks were also found in Mars' seismic data, and their characteristics and possible origins will be summarized. The InSight mission has successfully explored the structure of Mars' crust, while the exploration of Mars' deep interior is still limited because there lacks large-magnitude Marsquakes and meteorite impact events.