In order to study fracture mechanics of high strength steel with the moderate thickness, fracture tests were performed on 10 plates with elliptical hole fabricated from high strength steel Q345 with the thickness of 16mm. The effect of the notch sharpness (the ratio of the length of short axis to that of long axis of elliptic hole, b/a) and the notch depth (the ratio of the length of long axis of the elliptic hole to the width of plate, 2a/w) on fracture model of high strength steel was examined. Test results show that the first crack initiates at the notch edge. The fracture ductility is lower for the specimens with the sharper notch (a smaller ratio b/a) and the deeper notch (a larger ratio 2a/w), and the point of crack load lies in hardening phase of load-displacement curve. The fracture ductility is higher for the specimens with the obtuse notch (a larger ratio b/a), and the point of fracture load lies in necking phase of load-displacement curve. The ultimate strength of notched plates is independent of the notch sharpness (b/a) and the notch depth (2a/w).