Provided is a wellhead pressure testing and seal examining device. The wellhead pressure testing and seal examining device comprises a leather cup shaft, a leather cup, a leather cup pressing cap, a connecting connector, a piston, a sealing shaft, a spring, a pressure regulating base, a rubber sleeve, a sealing sleeve, an inner pipe, a cone, a slip, a lower connector, a slip holder, a seal blocking, a return spring and a spring seat, low pressure seal examining and high pressure seal examining can be conducted on an installed blowout preventer on the scene, reliable working of the blowout preventer is guaranteed, piercing-caused leakages of the blowout preventer and the connecting position between the blowout preventer and a wellhead are avoided, non-leakage of the wellhead during blowout of an oil-water well is ensured, the oil-water well is under a controlling status, personal injury and death and property loss are avoided, and remarkable economic benefit is achieved. According to the wellhead pressure testing and seal examining device, anchoring in a casing pipe can be conducted during the high pressure seal examining, so that axial force generated by the high pressure during the seal examining is supported on the casing pipe, and all parts are not damaged due to the excessive axial force.