The invention discloses a method for detecting and repairing a cycle slip by utilizing a BeiDou three-frequency observed quantity. The method mainly comprises the following steps of: 1, performing linear combination by utilizing the three-frequency observed quantity under the condition of providing a three-frequency signal by a BeiDou satellite navigation system, and constructing a combination noise detection quantity by selecting proper combination coefficients to detect the cycle slip; 2, after the cycle slip is detected, calculating and screening to obtain three sets of combination coefficients with superior performance in a pseudo-range carrier phase combination method, and calculating and repairing the cycle slip by utilizing the pseudo-range carrier phase combination method; and 3, finally, performing verification on a cycle-slip repairing effect by utilizing the combination noise detection quantity. The method for detecting and repairing the cycle slip is not related to the motion state of a carrier, can be used for reliably detecting and repairing the minimum cycle slip of which the time of losing lock reaches up to 30 seconds and can be used for detecting and repairing the cycle slip by the zero-difference, single-difference or double-difference carrier phase observed quantity when static measurement or dynamic measurement is performed.