Abstract: Objective Considering that is difficult to repair cycle-slips on each frequency in a triple-frequency ge-ometry-free phase combination a new method based on the linear combination of GNSS triple-frequen-cy un-differenced observations has been proposed to detect and repair cycle-slips.According to appro-priate principles,triple-frequency pseudorange observations and phase observations are respectivelyused to form different effective geometry-free linear combinations.The threshold of each combinationfor cycle-slip detection is deduced.The performance of this new method is analyzed systematically todetect big jumps,small jumps and special jumps,respectively.After rounding the big cycle-slips andrepairing observations,a searching method was used to repair small cycle-slips.At last,GPS triple-frequency data were used to verify the correctness of the algorithm.The results show that the pro-posed algorithm can simply and instantaneously detect and repair all possible cycle-slip combinations atevery frequency.