The invention provides a stop valve. The stop valve comprises a hollow valve seat, a valve element and a sealing ring, wherein the valve element is installed in the valve seat, the peripheral face ofthe valve element is provided with an annular sealing groove, and the sealing groove is internally provided with a first limiting part; and the sealing ring is installed in the sealing groove and abuts against the inner wall of a valve element hole, the sealing ring is provided with a second limiting part, and the second limiting part can coordinate with the first limiting part so that the sealingring can be limited into the sealing groove. By means of the double positioning of the sealing groove and the sealing ring and the first limiting part and the second limiting part, the sealing ring is reliability located in the sealing groove, the situation that due to excessive friction of the sealing ring and the valve seat, the sealing ring disengages from the sealing groove is avoided, then,the situation that when the sealing ring softly seals the inner wall of the valve element, the sealing ring deforms is avoided, the soft sealing reliability is improved, refrigerant leakage is avoided, the refrigerant charging amount of an air conditioner is guaranteed, and then the using performance of the air conditioner is guaranteed. The invention further provides the air conditioner.