The invention provides a post-cast strip baffle, a post-cast strip baffle support system and an erection method of the post-cast strip baffle support system, and belongs to the field of building construction. The post-cast strip baffle comprises a vertical baffle, wherein a row of reinforcing steel bar guide grooves are formed in each of the upper edge and the lower edge of the vertical baffle; the reinforcing steel bar guide grooves comprise reinforcing steel bar guide sections and reinforcing steel bar positioning sections. The post-cast strip baffle support system is of a structure that the post-cast strip baffle is erected on a bottom mold plate and is matched with reinforcing steel bars at a post-cast strip. The erection method of the post-cast strip baffle support system comprises the steps of putting the post-cast strip baffle between two rows of reinforcing steel bars, and rotating, so as to match the reinforcing steel bars with the reinforcing steel bar guide grooves. The post-cast strip baffle has the benefits that two procedures of bonding the reinforcing steel bars and erecting the baffle are not interfered by each other, the positions of the reinforcing steel bars can be effectively guided and corrected, the post-cast strip cast by using the baffle is tidy in cross section and the cross section is formed in a tongue-and-groove manner which is beneficial to water resistance of the post-cast strip; by adopting the scheme, the post-cast strip baffle is simple in structure and convenient to manufacture and mount, can be repeatedly used, and is remarkable in economic benefit.