A support base for a child safety seat includes a shell body configured to support a child seat, and a belt restraining frame pivotally connected with the shell body. The belt restraining frame includes a transversal portion, two side portions, and a middle portion located between the two side portions, the two side portions and the middle portion being fixedly connected with the transversal portion and having respective ends pivotally connected with the shell body. The belt restraining frame is rotatable relative to the shell body between a release position where the middle portion rises away from the upper surface of the shell body, and a clamping position where the middle portion is adjacent to the upper surface for pressing against an anchoring belt that is routed transversally across the shell body.