The utility model discloses an automatic sampler of a coulometry micro water tester and a sampler sampling assembly. The automatic sampler comprises a pipette, wherein a component in the pipette comprises a push button, a piston rod, a housing, a piston, a spring and a tip unloading button; a spearhead is arranged at the bottom end of the housing; the automatic sampler also comprises a sampler sampling assembly in any one of the technical scheme disclosed by the utility model; and the sampler sampling assembly comprises a sucker and a metal needle head. The automatic sampler can set the volume of transferring insulating oil in advance, and just needs two steps of loosening the button to suck the insulating oil and pressing the button to release the insulating oil, so that the operation is simple and convenient, and large influence on the accuracy of the volume of transferring the insulating oil caused by fine deviation of artificial operation can be effectively reduced. The sampler sampling assembly is used for matching with the pipette to form a transferring and sampling device of the insulating oil in the coulometry micro water testing process, and the metal needle head is used for puncturing a silicone pad at the sample inlet of the coulometry micro water tester, thereby directly sampling.