A method for reading battery status of a portable computer that is powered by a battery and has an operation system which reads the status of the battery by a keyboard controller in accordance with a preset time reference. The operation system reads the current system time first which is then compared with the time value when the operation system previously reads the battery status. A time difference between the current system time and the previous time of reading is obtained which is compared with the time reference. If the time difference is greater than or equal to the time reference, the operation system actually reads the battery status and stores the status in a system memory. If the time difference is smaller than the time reference, the operation system simply retrieves the battery status stored in the system memory and feeds the status to the operation system.