Device and method for sampling formation fluid while drilling

The invention provides a while-drilling formation fluid sampling device and method, and relates to the technical field of formation fluid sampling, the device comprises a sampling barrel, a first piston and a second piston are slidably arranged in the sampling barrel, and the first piston and the second piston divide the internal space of the sampling barrel into a sample cavity, a nitrogen cavity and a formation fluid cavity; the nitrogen cavity is used for pre-filling nitrogen; the suction structure is arranged at one end of the sampling barrel, the suction structure is connected with the sample cavity, and the suction structure is used for extracting a sample and injecting the sample into the sample cavity; the problem that in the prior art, in the while-drilling formation fluid sampling process, it is difficult to ensure that the sample pressure cannot be reduced after a sampling tool obtains a sample and returns to the ground, and then it is difficult to ensure the fidelity of the taken sample is solved.