A microprocessor for metering electric energy, a microcontroller unit thereof, and a circuit and a method for metering energy accumulation. The circuit for metering energy accumulation includes a calculation-comparison circuit and a counter circuit that are connected. The calculation-comparison circuit is configured to: calculate an accumulation of a value of power in power consumption data and a value of current energy, and a difference between the accumulation and a preset threshold; output a flag bit, characterizing whether the difference being less than zero, to the counter circuit; set the value of current energy to be the difference in a case that the difference is not less than zero; and set the value of current energy to be the accumulation in a case that the difference is less than zero. Calculation in electric energy metering is specifically implemented, effectively improving electric energy metering efficiency and product economic benefit.