The invention discloses an openable kelly cock valve with a high pressure difference, which relates to petroleum machinery. The openable kelly cock valve comprises a valve body (1), a knob (2) and a valve ball (3), wherein the valve ball (3) is fixed in the valve body (1) by an upper valve seat (4) and a lower valve seat (5); the lower valve seat (5) is sleeved with a wave spring (6); an annular sealing portion (7) is arranged on the upper valve seat (4) and the lower valve seat (5) respectively and in contact with the valve ball (3) by an inner-side corner; the lower valve seat (5) and the annular sealing portion (7) thereof are of a split structure and in threaded connection; the wave spring (6) is abutted against the outer-side end of the annular sealing portion (7) of the lower valve seat (5). The openable kelly cock valve has the advantages of being simple in structure, reliable in sealing, and low in opening torque; manual opening is realized in case of building a pressure of 35MPa in a drilling tool, and manual rapid closing in case of a vertical tube pressure below 35MPa during overflow and well kick can be realized; the reliability of a blowout prevention operation in a wellhead and the safety of wellhead operations are improved.