Photometric study of the contact binary 07g-3-00820 at the period cut off

07g-3-00820 is a K-type contact binary system with a period of 0.2269551 days. This extremely short period makes this system a rare target whose period is close to the empirical limit (0.22 days). Rc and Ic light curves of this binary were obtained using the 1.0  m reflecting telescope at Weihai Observatory of Shandong University. A high mass ratio of q = 1.300 ±  0.006 and a low contact degree of f=5%±1.5% were determined from a photometric study using the Wilson-Devinney method. The following parameters of this W-subtype shallow contact system were derived: M1=0.621±0.072M⊙,M2=0.807±0.093M⊙,R1=0.634±0.036R⊙,R2=0.710±0.037R⊙,L1=0.270±0.037L⊙, and L2=0.339±0.048L⊙. By analyzing the location of the two components on the mass-luminosity diagram, we provide a preliminary discussion on the properties and the state of evolution of this system.