The utility model relates to an eccentric well testing device, and belongs to the technical field of oil field oil production machinery. The eccentric well testing device comprises a flange and fastening pieces. Flange through holes corresponding to through holes of a four-way well mouth flange are formed in the flange. A circular through hole is formed in the center of the flange. A mouth which sequentially penetrates through the circular through hole and the edge of the flange in the radius direction is formed in the flange. The flange and the four-way well mouth flange can be fixedly connected through the fastening pieces by means of the flange through holes and the through holes of the four-way well mouth flange. By installing the flange used for tests on the well mouth of an eccentric well where no well mouth flanges are installed, a pulley block can be installed on the well mouth of the eccentric well, and the problems that in the prior art, in the testing process, the stability of the pulley block is low, the testing cost is high, and the testing safety is low are solved; the effects of conducting related tests on the eccentric well where no well mouth flanges are installed can be achieved with low cost, high stability and high safety.