The photocatalytic degradation of tetracycline by Si-doped Li₂SnO₃ was investigated. The results show that, through iso-electron Si doping the optical absorption band gap of Li₂SnO₃ may be reduced, while its optical absorption coefficient is increased, in consequence, the photocatalytic degradation efficiency of the Si-doped Li₂SnO₃ for_{tetracycline is enhanced. The isoelectronicaly Si-doped Li2SnO3 is a pure and irregular mass solid, and its lattice parameters tend to decrease with the increase of Si doping amount. The photocatalytic performance of the Si-doped Li2SnO3 was significantly improved by Si doping. Under UV irradiation for 25 min, the photocatalytic degradation efficiency of tetracycline by the Si 10%-doped Li2SnO3 is 75.8%, which is about twice as that by the simple Li2SnO3. The photocatalytic degradation behavior of Si-doped Li2SnO3 conforms to the pseudo-first-order kinetic model, and the fitting rate constant is 0.02464 min^-1. The Si-O bond formed on the top of the valence band of Si-doped Li2SnO3 reduces the optical absorption band gap and enhances its optical absorption capacity. The photocatalytic degradation mechanism of Si-doped Li2SnO3 is cave-dominated.}