A new strategy of cloning uncompatible DNA ends was reported here with the example of cloning of pC/C and C gene of hepatitis B virus. When the terminals of DNA fragments digested by restriction enzymes are blunt ends, they can be formed into tails with a single 3′ adenosine overhanged by modified with template-independent terminal transferase activity of Taq polymerase in reaction buffer containing dATP. Furthermore, if the DNA fragments have 5′-protruding sticky ends, these terminus can be filled into blunt ends with 5′ to 3′ Taq polymerase activity in the existence of dNTP, and then again added a single adenosine at their 3′ ends by the transferase activity of Taq polymerase. The fragments modified as such above-mentioned can be easily subcloned into T vector.