In order to improve the power factor of the new large transformer in no-load operation and realize it economic operation,we have analyzed of transformer in no-load loss generated , fund out the reason of the reducing transformer power factor and Sput forwardSa method which is based on the field current reactive compensation to improve the power factor of transformer under the no-load condition.Through introducing Matlab simulation modeling of transformer under the no-load running and analyzing the field data analysis during commissioning, the power factor obviously improved and reached the appraisal of the power factor requirements. The content of the described in this article has been applied to the actual operation of the transformer, and achieved good results.