The quantum voltage standard based on the Josephson effect has been applied in AC power measurement. Differential sampling is the most promising method for measuring AC signals based on quantum technology. In this paper, we developed an AC power measurement system based on differential sampling and analyzed the system error sources through simulations and experiments. The system error comes from the sampling rate, step number of stepped waves, phase difference, and sampling time. The traceability of power to quantum voltage using differential sampling technology was achieved with an uncertainty of 10-6.