The purpose of the paper was to investigate the effects of four test conditions on tensile bond strength to dentin, which included: (1) the area of tooth bonded, (2) tensile speed, (3) the fresh degree of tooth, (4) the times of tooth used. For GP dentin bonding agent, the results indicated: 1. There was no obvious effect of the bonded area on the bond strength. Both occlusal face and buccal face could be adopted. 2. There was no evident effect of the tensile speed on the bond strength. Any tensile speed could be chosen within some extent. 3. The bond strength greatly depended on the fresh degree of tooth. The longer the period of tooth stored after extraction was, the lower the bond strength was. Tooth used should be within 1 month after extraction. 4. There was obvious relationship between the bond strength and the times of tooth used. The more the tooth was repeatedly used, the lower the bond strength was. Tooth might only be used once.