The hydrosilylation of alkenes in a supercritical CO₂ (scCO₂)/ionic liquid (IL) system was investigated. Rh(PPh₃)₃Cl exhibited excellent catalytic activity and selectivity. KO^tBu was used as an additive, and no hydrogenation by-product (alkane) was detected in the scCO₂/IL system. During hydrosilylation in the scCO₂/IL system, the reactants were possibly transferred into the IL phase by scCO₂, in which the catalyst was dissolved. The products can be flushed with scCO₂ after the reaction and the catalyst/IL system reused.