The invention discloses a pressure fluctuation buffer device which comprises an upper joint, a lower joint, a cylinder body, at least one separation plate, an upper cover plate and a lower cover plate. The upper end and the lower end of the cylinder body are fixedly connected with the upper cover plate and the lower cover plate respectively, the lower end of the upper joint stretches into the upper cover plate and is fixedly connected with the upper cover plate, the upper end of the lower joint is fixedly connected with the lower cover plate, the separation plates are transversely arranged in the cylinder body, and divide the interior of the cylinder body into cavities of which the volumes are increased from bottom to top, throttling holes communicated with threaded sinking holes are formed in the lower end of the upper joint and the upper end of the lower joint respectively, and throttling holes are also formed in the separation plates. The device is simple in structure, low in cost and convenient to assemble and disassemble, effectively slows down pressure fluctuation in a diesel engine fuel tube, and prolongs the service life of measuring elements like a pressure gauge.