The invention discloses a tamping mechanism for sidewall concrete in the tunnel secondary lining molding process. The tamping mechanism comprises an elastic winding drum, a flexible shaft and guide apparatuses, wherein one end of the flexible shaft is wound on the elastic winding drum, and the other end is used for being connected with a vibrating and tamping rod; a plurality of guide apparatusesare provided, respectively welded on the inn wall surface of an edge template of a template trolley, disposed between the elastic winding drum and a pouring window at the bottom of the template and distributed from top to bottom; the flexible shaft passes through each guide apparatus successively until the vibrating and tamping rod is inserted into the concrete being poured. The problems of high cost, low efficiency and low safety for tamping the side wall concrete can be well solved.