A whispering gallery mode microsphere resonator is proposed and demonstrated. The device is fabricated by splicing a single-mode fiber with a capillary tube and, by properly adjusting the discharging current and the splicing position of the fiber and capillary tube, an expanded hollow sphere cavity is formed at the splicing junction. A microsphere is inserted into the hollow sphere cavity and positioned in close touch with the cavity wall to excite whispering gallery mode resonance via the coupling of evanescent field of the anti-resonant reflecting guidance mode produced in the cavity wall. The device has a quality factor of 3.725 ′ 10_³ and is compact, simple in fabrication, easy in packaging, convenient in operation and of low cost.