The invention discloses a well head sampling method of an oil and gas well. The well head sampling method includes the steps that formation fluid flowing in the horizontal direction is changed into formation fluid flowing in the vertical direction through a sampling device; in the vertical direction, it is achieved that uneven-flowing fluid is changed into even distribution and flowing fluid through a filtering and mixing device; after the fluid evenly flows, a certain quantity of samples are sampled at different positions of a circulation channel through a stretchable sampling probe till a special sample bottle is full. Under the condition that the well head sampling condition meets PVT analysis of a laboratory, underground fluid samples can be completely replaced with the samples sampled with the sampling method, the sampling time is set during stable-flowing finding production, and meanwhile getting of capacity data of the oil and gas well is not influenced; compared with an underground fluid sampling method, according to the well head sampling method, the operation time is not additionally occupied, a special sampling tool is not required, the operation time of a whole well is saved, and operation cost is reduced.