A support base for a child safety seat includes a shell, a belt clamp and a latching mechanism. The shell is adapted to receive a child seat thereon, and has a belt anchoring region including a first surface and a second surface. The belt clamp is pivotally connected with the shell, and is operable to clamp a first belt portion and a second belt portion respectively adjacent to the first surface and the second surface. The latching mechanism is operable to lock the belt clamp in a clamping state.