The invention discloses a microwave light source which comprises a waveguide tube. A quartz bulb case is arranged at the orifice of the waveguide tube and is filled with an operation material. A fan outlet is communicated with an air inlet formed in one side of the waveguide tube; and a magnetron is coupled to the lower end of the waveguide tube. According to the invention, with the spherically symmetric quartz bulb case, the quartz bulb case floats in the air and is driven to rotate by using the aerodynamics. On the basis of the simple and ingenious design, the rotation cooling need of the quartz bulb case is met. Meanwhile, the quartz bulb case has good symmetric and beautiful effects; and the floating design is novel.