The stator winding of hydraulic generator is flexible and can be lap winding or wave winding according to the engineering experience. In order to restrain the generator's vibration attributed to rotor eccentricity， lap winding or centralized arrangement wave winding is adopted by a series of large-sized hydraulic generators recently， but their main protection performance is harmful to the generators' safe operation. By using the quantitative and optimal design methods of main protection for large-sized hydraulic generators， internal fault feature and main protection performance of lap winding generators with different rotational speeds are analyzed and compared based on the overall quantitative analysis. New suggestions on stator winding design of large-sized hydraulic generators are presented in this paper， they are， firstly， selecting lap winding for the hydraulic generator with high rotational speed can meet the requirements of electric machine design and relaying protection simultaneously; and secondly， above stator winding type used for the hydraulic generator with low rotational speed may lead to the remarkable increase of non-operation faults， which needs to be further investigated.