The catalytic properties in the hydrogenation of olefins and the stability of polymer-supported colloidal palladium catalysts prepared by a one-step preparation method (OSPM) have been investigated. The influence of the structure of the catalyst and solvents on the catalytic properties and stability were studied. A comparison of catalytic properties and stability between polymer-supported colloidal Pd catalysts prepared by different methods and also between polymer-supported and SiO2-supported Pd catalysts has been made. Experimental results show that the catalysts prepared by OSPM possess high catalytic activity for hydrogenation of olefins with low metal loss and good stability. Their excellent catalytic properties seem to arise from the highly dispersed and uniform dispersion of active metal, and also from the effective protection of the active metal by polymer. Proposals for the reducing loss of metal catalysts from supports are made.