The invention relates to an intelligent sine-wave-output uninterruptible power supply and an automatic control method, which belong to the technical field of power supplies. The device disclosed by the invention comprises a sampling detection circuit, a booster circuit, an inversion circuit, an output control circuit, a display alarm circuit, a communication circuit, an auxiliary power supply circuit, a charge control circuit and a single chip, wherein the single chip is connected with the sampling detection circuit, the booster circuit, the inversion circuit, the output control circuit, the display alarm circuit, the communication circuit, the auxiliary power supply circuit and the charge control circuit, the booster circuit is connected with the auxiliary power supply circuit and the inversion circuit, and the inversion circuit is connected with the output control circuit. The method disclosed by the invention comprises the steps of initializing; detecting a mains supply; starting communication, detecting overload information by the single chip through an ADC port, and when an overload phenomenon occurs, sending a shutdown signal by the single chip to stop working; repeatedly and cyclically executing programs, and detecting all the links of the whole circuit. The device disclosed by the invention is safe and reliable, high in output stability, and capable of reducing cost.