In the processing of sour natural gas, the conversion of hydrogen sulfide into elemental sulfur is often carried out using the modified Claus sulfur recovery process. In this work, the most important influencing parameters regarding the selection of the proper catalysts for Claus SRU (sulfur recovery unit) converters are technically evaluated. It is shown that the pore size and pore size distribution, size, shape, bulk density, mechanical strength and attrition resistance of the catalyst particles are the main parameters which should be considered in selection of Claus catalysts. The general classification of Claus catalysts and the most important specifications required for proper selection of converter catalysts are also presented.