The High Energy Photon Source (HEPS) is the first fourth-generation synchrotron radiation source that will operate in high energy region in China. The HEPS accelerator consists of a linear accelerator, a booster, a storage ring and three transfer lines. This paper presents important progress on the HEPS Linac. The 500 MeV Linac has been constructed using S-band normal conducting structures, including a thermionic cathode electron gun, beam bunching system, and main accelerating section. After completing the equipment installation and high-power RF conditioning, the beam commissioning was started on March 9, 2023. The beam was successfully transferred to the end of the Linac on the same day, and a beam with 500 MeV of energy and 2.5 nC of pulse charge was achieved within 5 days. As measured up to date at the Linac exit, the beam energy spread and energy stability are 0.4% and 0.06% respectively, and the horizontal and vertical geometric emittances are 233 nm and 145 nm, respectively. The maximum bunch charge reaches up to 7.0 nC. Further beam commissioning will be implemented to gain full performance of the Linac.