Ultrasonic methods were extensively used for non-destructive evaluation of wood. In this study, various degrees of wood decay in Luanta China fir standing trees (Cunninghamia lanceolara var. Konishii form. Konishii) damaged by squirrels were assessed. Transverse traversing time was measured with on ultrasonic method using PUNDIT and SYLVATEST ultrasonic meters. Results show that the biological internal quality of standing trees can he evaluated by measuring the ultrasonic traversing time on the radial axis of tree trunks. Effects of decay on the traversing time of standing trees are discussed. Results also show that the ratio of traversing time in the 90° direction to radial (180°) direction for seriously decayed trees are between 0.207 and 0.517. If the ultrasonic traversing times are higher, then the trees are decayed within the same diameter class. Results verified that the internal decay of tree can be detected using ultrasonic measurements the radial direction. Experimental results suggest that the non-destructive testing (NDT) of standing trees can be applied to salvage cuttings, and that ultrasonic traversing time along the radial direction can serve as a guideline to distinguish the internal physical status of standing trees.