The invention relates to a method for preparation of ruthenium-based carbene catalysts with chelating alkylidene ligands (so-called “Hoveyda-type catalysts”) in a cross metathesis reaction by reacting a ruthenium-alkylidene complex with an olefin derivate in the presence of a polymer-supported cation-exchange resin (PSR) acting as a ligand (i.e. phosphine or amine) scavenger. Preferably, penta-coordinated ruthenium benzylidene or indenylidene carbene complexes are employed. The polymer-supported cation-exchange resin (PSR) may be an acidic resin (comprising sulfonic acid or carboxylic groups) or a resin containing carboxylic acid chloride (—COCl) groups or sulfonyl chloride (—SO2Cl) groups. The process is versatile and environmentally friendly; high yields are obtained.