Lead-free halide perovskites have triggered appealing interests in the field of optoelectronics and photocatalysis due to their low toxicity, tunable optical and charge carrier properties. For the application point of view, it is desired to develop stable lead-free halide perovskites with multifunction. Herein, we successfully developed a series of Cs 2 Pt x Sn 1-x Cl 6 (0≤x≤1) with high stability, which show switchable photoluminescence and photocatalytic functions by varying the amount of Pt 4+ substitution. The Cs 2 Pt x Sn 1-x Cl 6 solid solution with dominant proportion of Pt 4+ shows broadband photoluminescence with lifetime in microsecond-timescale. The Cs 2 Pt x Sn 1-x Cl 6 solid solution with small amount of Pt 4+ substitution exhibits photocatalytic hydrogen evolution activity. Optical spectroscopy study reveals the switch between photoluminescence and photocatalysis function is controlled by sub-bandgap states. Our finding provides a new way to develop lead-free halide perovskites with multifunction and high stability.