Disclosed is a catalyst for the polymerization of olefins comprising thienyl-substituted silanes, which comprises a solid titanium catalyst component containing titanium, magnesium and a halogen as the main components, an alkylaluminum compound, and a component of organosiloxane compound comprising two thienyl as substituents represented by general formula (I). The molar ratio of each catalyst component is 1:50-150:5-50 based on titanium:aluminum:silicon. When the catalyst is used in the polymerization of propylene, the polymerisate obtained has a very high degree of isotacticity, and the yield is high.