In the background of energy change and digital revolution, Smart Meter with traditional metrology, fee control and communication cannot support the development demand anymore. The paper design a smart IoT electricity meter with ‘multi-core, modular’, push out standard interfaces, supports power, communication and raw data for kinds of modules, can meet varies application demand of electricity customers. Use the power quality analysis application as use case, design a functional extend module, then test the function and verify the data accuracy by experiment test.