The invention provides a fault detection method and a fault detection device for a satellite-simulated sun sensor. The method comprises the following steps: acquiring telemeasuring data of a sun sensor in a current period; according to the telemeasuring data, determining whether the working mode of a satellite in the current period is a predetermined model or not, if so, calculating the predicted value of an output angle of the simulated sun sensor by means of a combined diagnostic mode; and judging whether the simulated sun sensor has faults or not in the current period according to the predicted value and a telemeasuring value, including an output angle, of the telemeasuring data. According to the embodiment of the invention, the predicated value of the output angle is calculated by means of the combined diagnostic mode; whether faults exist is quantitatively diagnosed by combining the predicted value and the telemeasuring value, including an output angle, of the telemeasuring data, and abnormal changes of the telemeasuring value are immediately and quickly found, so that the precision and reliability of satellite in orbit autonomic diagnosis and ground measuring data judgment are improved. The method and device are matched with a satellite control module, and are high in adaptability and universality, thereby laying a good foundation for intelligent autonomic diagnosis of the satellite.