Through　the　introduction　of　green　finance　policies,　governments　hope　to　improve　the　guiding　role　of　institutional　investors　in　green　investment　and　provide　financial　support　for　green　enterprises.　Using　the　data　in　China,　the　difference-in-difference　(DID)　analysis　explores　whether　the　implementation　of　policies　could　change　institutional　investors＇　attitude　to　environmental　factors　when　making　investment　decisions.　Considering　the　effect　of　investment　horizons,　we　find　that　long-term　institutional　investors　have　shown　symmetric　preferences　on　green　investment,　while　short-term　institutions　are　more　affected　by　green　finance　policies.　Additionally,　the　mechanism　analysis　shows　that　green　finance　policies　can　influence　the　green　investment　of　institutional　investors　not　only　by　affecting　stock　price　returns　but　also　by　increasing　the　innovation　capabilities　of　green　companies　and　thus　improving　corporate　performance.　Besides,　heterogeneity　and　moderating　effect　analyses　find　that　green　finance　policies　can　achieve　better　policy　effects　when　financial　institutions　invest　in　non-state-owned　enterprises,　enterprises　with　higher　quality　of　information　disclosure　and　poor　external　supervision.　The　finding　would　extend　the　studies　of　green　investment　in　emerging　markets　and　present　new　evidence　about　the　policy　effect　on　institutions＇　preferences　for　green　investment.