The present invention relates to a wellhead coalbed gas sampling apparatus, which comprises a bottle, wherein the first end of the bottle is provided with a first end cover in a sealing manner, the second end of the bottle is provided with a second end cover in a sealing manner, the first end cover is provided with a first unidirectional outlet joint forming unidirectional conducting from the internal of the bottle to the external of the bottle, and the second end cover is provided with a second unidirectional outlet joint forming unidirectional conducting from the internal of the bottle to the external of the bottle, and a unidirectional inlet joint forming unidirectional conducting from the external of the bottle to the internal of the bottle. According to the present invention, the sampling apparatus is full of pure water and is connected with the wellhead gas pipe so as to complete the sampling operation without additional auxiliary equipment, such that the sample pollution during the gas sampling and the experiment is not easily caused, and the experimental precision is improved; and the sampling apparatus can be directly connected with the laboratory testing equipment, and has the good sealing property.