The utility model discloses a combined thermometer for a bioreactor and the bioreactor, and relates to the technical field of biology. The sheath comprises a sheath main body, a mounting hole is formed in the sheath main body, and a thermometer is arranged in the mounting hole; a first sealing ring is further arranged at one end of the sheath body, the inner side of the first sealing ring abuts against the thermometer, and the outer side of the first sealing ring abuts against the sheath body. A locking piece is arranged at one end, close to the first sealing ring, of the sheath main body, anda locking hole for a thermometer to penetrate through is formed in the locking piece; the locking piece is used for being arranged on the sheath body in a sleeving mode and tightly pressing the firstsealing ring on the sheath body and the thermometer. The glass bulb end of the thermometer can be directly arranged in the bioreactor and is in direct contact with liquid in the bioreactor, so that the detection sensitivity and accuracy of the thermometer are improved, and the calibration and measurement accuracy of the temperature detection system is improved.