For the issues of detecting insensitive cycle-slip in GNSS signals, this paper analyzes the generation and distribution of insensitive cycle-slip in three-dimensional coordinate system, researches the influence of the detection threshold on detecting insensitive cycle-slip, and then studies the effect of combined detection of combinations. A combination coefficient selection method is proposed for detecting insensitive cycle-slip. This method builds a function model based on the detection amount of combined coefficient, and screening the most sensitive combination coefficients. The method can detect insensitive cycle-slip with similar hop variables at three frequencies. As verified by the BeiDou triple-frequency measured data, multiple GF combinations effectively increase the detection probability of insensitive cycle-slip, and the appropriate number is two. The combination selected by proposed method effectively detect the manually added insensitive cycle-slip.