A catalyst component (A) for olefin polymerization is prepared by contacting a solid component (a) containing magnesium, titanium, halogen and an internal electron donor compound with an organosilicon compound (b), wherein the organosilicon compound (b) is one or more selected from a Si—H functional group containing chainlike polysiloxane (b1) represented by formula (Ix), a cyclic polysiloxane (b2) represented by formula (Iy) and a Si—H functional group containing organosilicon compound (b3) represented by formula (Iz). In addition, a process for preparing the catalyst component and the corresponding catalyst is described. The catalyst component and its catalyst have high catalytic activity, good hydrogen response, and good stereospecificity, the catalyst can release its activity more evenly, and the obtained polymer has significantly increased bulk density. The definitions of R1 to R10, n and z in the formulae (Ix), (ly) and (Iz) are as described in the specification.