The invention discloses an ejecting device capable of being automatically opened. The ejecting device capable of being automatically opened comprises an ejecting head, an ejecting pipe, a valve core, a connecting pipe and an elastic piece, wherein the ejecting head is provided with an ejecting head cavity and an ejecting opening which is communicated with the ejecting head cavity, the inner wall of the ejecting head cavity is provided with a valve base, the front end of the ejecting pipe and the back end of the ejecting opening are communicated and connected in a sealing mode, the front refers to the ejecting direction, the valve core is located inside the ejecting head cavity and the ejecting pipe, the valve core moves front or back inside the ejecting head cavity and the ejecting pipe to be matched with or separated from the valve base, the front end of the connecting pipe is located inside the ejecting pipe, and the elastic pipe exerts a force to enable the connecting pipe to move toward the valve base on the connecting pipe. A trigger is not needed, the match of the valve core and the valve base is separated when liquid inside the ejecting device is boosted to a certain value, and the automatic opening of the ejecting device is realized. The ejecting device capable of being automatically opened is simpler in structure, an operator can stand at the position of being far from the ejecting field, and the operation of opening the ejecting device can be conducted through the boosting of a liquid supply device of the ejecting device.