Steel plates strengthened by carbon fibre-reinforced polymer (CFRP) sheets were extensively studied because they can be utilized to strengthen deficient structures with irregular shapes. Although the effective bond length for strengthening plain steel structures is well known, the effective bond length for deficient steel plates remains unclear. In addition, debonding failure is a critical issue that limits the widespread application of this technique. Considering these problems, the tensile behaviour of steel plates with and without notches strengthened by CFRP sheets was experimentally studied in this paper. Semi-circular notches were created at the centre of the steel plates. CFRP sheets with different bond lengths were applied for strengthening. Furthermore, to prevent debonding failure, a G-shaped anchorage system was applied. As observed, the bond strength increased with the bond length until the bond length exceeded 400mm. For specimens with notches in the centre, a stress concentration formed near the notch where the debonding initiated. After applying the anchorage system, the bond strength improved significantly, but debonding failure was still observed. Thus, the bond length for a steel plate with defects could be longer than that for a plain steel plate, and the weak point is the point in the specimen that undergoes the greatest change in stiffness. More importantly, the G-shaped anchorage system effectively resisted the increase in normal stress and improved the bond strength. However, due to insufficient shear stress resistance, the system ultimately could not prevent debonding and needs further improvement.