The generators of 1 036 MW ultra-supercritical unit in Haimen power plant use the single-ring type sealing oil system. A method was proposed for hydrogen leakage determination without collapsing sealing oil bearings, based on the clearance changes or damage degree of seal tile by measuring the oil leakage weight of seal tile, under the running condition of loading, 3 000 r/min or turning. This simple and feasible method can be used as a reference for the hydrogen leakage determination of other similar units.