At room temperature, efficient second harmonic generation (SHG) emission is observed in thin ZnO crystal hollow rods (tubes) with diameter∼0.2 mm under the excitation of femtosecond laser from 700 to 860 nm. Power and polarization dependence of the SHG signal on the primary excitation beam is also measured. The multiple total reflections between the outer and inner surfaces of the sample are analyzed to be responsible for the efficient SHG. Ninefold amplification of SHG signal in the tube structure is estimated. © 2011 American Institute of Physics.