The present invention provides a loading calculation method and a loading calculation system for a processor in an electronic device is disclosed. The loading calculation system comprises: a detecting unit, a determining unit, a generating unit, and a calculating unit. The loading calculation method comprises: detecting a plurality of switching actions of the processor to generate a detecting result; determining a time interval to separate the detecting result to generate a plurality of time periods; generating a log file of scheduling according to the detecting result and the plurality of time periods; utilizing the processor for enabling the log file of scheduling; and calculating the processor loading according to the log file of scheduling.