The electrical performance of transmission line insulators will decrease dramatically under ice-covered conditions, and ice flashover may occur under operating voltage. There is no direct and effective monitoring method for ice cover on insulators of transmission lines. In this paper, the interface quasi-distributed fibre Bragg grating (FBG) is used to study the positioning detection of glaze icing loads on composite insulators, and a mechanical lever model of single glaze icing load on single umbrella detection with three FBGs is established. Based on this model, a multi-glaze location detection method on multiple umbrella skirts is proposed. Six optical fibres with 13 quasi-distributed FBGs each are implanted into the interface of a 110 kV composite insulator. The minimum load test of FBG for detecting glaze icing load, the FBG axial/circumferential sensing rule test for the glaze, and the weight simulation test and laboratory icing verification test for multi-glazes on multi-umbrellas location detection method are carried out. The results show that the positioning of glaze simulated by weights is accurate, and the positioning of icing in the laboratory is basically correct.