Abstract: At present,the electrical test of the whole set of medium and large thermal power generating units before start-up is carried out in accordance with Procedure for Trial Operation and Acceptance of Thermal Power Generation Construction Project:DL/T 5437—2009 and Procedure for Preventive Test of Electric Power Equipment:DL/T 596—2021,but the conventional electrical test method cannot meet the safety requirements of equipment in extreme environment in extremely cold regions. The influence of low temperature factor on the equipment and facilities of the generator set during the trial operation of the whole set of thermal power plant equipment in extremely cold regions is avoided by optimizing short-circuit test,homologous nuclear phase test and simultaneous test based on the case study of the whole set start-up trial operation of a 600 MW large thermal power generating unit.