The invention relates to a superficial tumor ultrasonic thermotherapy system guided by magnetic resonance. The superficial tumor ultrasonic thermotherapy system guided by the magnetic resonance is used to observe and control the temperature of a focus target area of a superficial tumor. The superficial tumor ultrasonic thermotherapy system comprises a main control unit, a power ultrasonic transducer exciting unit, a cooling unit, an ultrasonic transducer, a magnetic resonance imaging (MRI) scanning unit and a MRI temperature processing unit. The main control unit is respectively connected with the power ultrasonic transducer exciting unit, the cooling unit, the MRI scanning unit and the MRI temperature processing unit. The power ultrasonic transducer exciting unit is sequentially connected with the ultrasonic transducer, the focus target area, the MRI scanning unit and the MRI temperature processing unit. The cooling unit is connected with the ultrasonic transducer. The superficial tumor ultrasonic thermotherapy system enables MRI and ultrasonic thermotherapy technology to be combined, so that quantification, real-time and accurate controlling of the therapeutic process of ultrasonic thermotherapy can be achieved. Compared with the prior art, the superficial tumor ultrasonic thermotherapy system guided by the magnetic resonance has the advantages that undamaged, real-time and accurate treatment to the superficial tumor can be achieved, mounting is simple, cost is low and the like.