Larch lumbers were tested by using modal analysis technology and Frequency response functions (FRF) were derived. Modal parameters, including first 4 intrinsic frequency and first 3 modal shape, were distinguished by single modal method. Research shows that the intrinsic frequency of hole-defect lumbers is little lower than standard lumbers’ and the change rate of frequency is becoming larger gradually with the diameter of hole-defect. However, it can not judge the position of the hole-defect by the change rate of frequency. The modal shape of the node near the hole-defect always jumps abruptly, so it can estimate the particular position of hole-defect in the lumber. The variation of modal shape is becoming larger gradually with the diameter of hole-defect. It can make qualitative and quantitative estimate to the hole-defect in the lumber by considering intrinsic frequency and modal shape together.