A child tray assembly includes a first tray and a second tray. The first tray is slidably disposed on a child seat. The first tray includes a first tray body and a first actuator. The second tray is detachably disposed on the first tray. The second tray includes a second tray body, a second actuator and a sliding latch. The second tray body can be installed on the first tray body by a first engaging portion of the sliding latch. The first actuator can be driven by the second actuator to allow the first tray to slide relative to the child seat when the second tray is disposed on the first tray. Furthermore, lower tubes can be installed on the second tray body by a second engaging portion of the sliding latch to form a small table when the second tray is detached from the first tray.