AbstractThis study investigated several key mechanical and physical properties of oriented strand board (OSB) made from China fir strands impregnated with phenol-formaldehyde (PF) resin. Results showed that accumulated percentages of strand alignment angles between strand length direction and mechanical alignment direction on OSB face and bottom layer were within 0° and 30° vs. 88.2% and 76.2%, respectively. Ultrasonic velocity at 0° strand angle (V0) was the highest, decreasing rapidly with increasing aligned angle (θ). The lowest ultrasonic velocity was found at 90° of strand’s angle (V90). The relationship between θ and V could be represented by Hankinson's formula, where the optimal n exponential values were between 1.59 and 1.88. The anisotropic properties of the OSBs, defined as the ratio of V0/V90, were 2.23 to 2.45 for the bending specimens. The ratios of MORp/MORv and MOEp/MOEv were 3.79 to 4.15 and 4.18 to 5.42, respectively. Effects of PF-impregnation on the bending properties showed superior performance. The parallel bending strength (MORp) was 64.7 to 84.8 MPa and the MOEp was 13.0 to 15.9 GPa, respectively. After accelerated deterioration testing, the retention rates of MORp and MOEp (%) were 78.3% to 88.2% and 68.0 to 83.1%, respectively. Further, the dimensional stability of PF-impregnated OSB showed good performance in thickness swelling (TS) and linear expansion (LE).