A connecting device for a child carrier, a child carrier and a child crib are provided. The child carrier includes a carrier body and an accessory, the carrier body including at least one first rod, the accessory including at least one second rod. The connecting device is configured to connect the accessory to the carrier body and includes: a fixing base connected to the second rod and configured to accommodate the first rod; an operating member slidably connected to the fixing base; and an engaging member connected to the operating member. The sliding of the operating member along the fixing base is capable of driving the engaging member to be switched between a locking position and an unlocking position.