An experiment was conducted to Korean pine specimen by ultrasonic tester. The effect of hole size and holes amount in axial direction of wood as well as the distribution of end holes on ultrasonic wave velocity were respectively studied. A comparison test was carried out between the specimens of one hole defect and no defect with different lengths. Then regression analysis of the relation between hole size and ultrasonic wave velocity was done using SPSS software. The experimental results show that the length of wood components has significant effect on ultrasonic wave velocity. The ultrasonic wave velocity has negative correlation with hole size and holes amount. End hole has no significant effect on ultrasonic wave velocity. This research will provide some theoretical basis for the detection of internal defects in wood materials, material evaluation and the evaluation of physical and mechanical properties testing.