The present invention discloses a 0.2S-class three-phase power meter based on wide-range synchronous measurement. The power meter comprises a central processing unit, an analog-digital converter, and a field-programmable gate array, a digital signal processor, a storage, a constant-temperature crystal oscillator and a clock chip which are connected with the central processing unit, the field-programmable gate array is connected with the digital signal processor, the field-programmable gate array and the digital signal processor are connected with the analog-digital converter, and the central processing unit is configured to externally connect with the clock synchronizing system taking the pulse per second as the standard or the IEEE 1588 protocol clock system of an intelligent substation. The present invention further discloses a method for measurement of a traditional transformer substation and an intelligent substation through adoption of the 0.2S-class three-phase power meter based on the wide-range synchronous measurement. The 0.2S-class three-phase power meter based on wide-range synchronous measurement and the measurement method thereof can perform synchronous measurement of instantaneous values of electrical parameters to satisfy requirements of wide-range measurement.