Sun-tracking method and system for disc solar-thermal power generating system

The invention discloses a sun-tracking method for a disc solar-thermal power generating system. The solar-thermal power generating system comprises a light focusing disc (20) and a heat collector (10); the sun-tracking method comprises the following steps of: 1) acquiring temperature distribution information of the heat collector (10); 2) judging whether incident rays of the sun are completely focused after passing through the light focusing disc (20) according to the temperature distribution information, if yes, performing a step 10), otherwise, performing a step 3); 3) acquiring a current angle of the light focusing disc (20) and a needed target angle for the light focusing disc (20) in a complete focusing process, and adjusting the current angle of the light focusing disc (20) to the target angle; and 10) keeping the current angle of the light focusing disc unchanged. The method achieves accurate tracking for the sun, strengthens light focusing precision of the incident rays of the sun. The invention further provides a sun-tracking system corresponding to the sun-tracking method.