A socket connector (1) includes a base (2), a cover (3) slidably mounted on the base, and an actuator (4) for actuating the cover to slide on the base between a pin insert position and a second engagement position. The base comprises a mainbody (21) and a fixing portion (22) in front of the mainbody. The mainbody defines a plurality of passageways receiving a plurality of terminals therein, and the fixing portion has blocks thereon. The cover comprises a body portion (31) and a header portion (32) in front of the body portion. The body portion defines a plurality of through holes provided in a one-to-one corresponding relationship with the passageways of the underlying base. The header portion is fitly fixed on the fixing portion of the base and engaging with the blocks thereof for preventing the cover from sideways rotation moving.