Investigation shows that one of the failure modes of HDPE pipe is the crack slowly grows across the thick direction and leads to failure at last. So that it is very important to study the resistance to crack initiation properties of HDPE pipe and its butt-fusion welded joint. The J-integral is applied to character the fracture initiation of a tough polymer for which the concept of linear elastic fracture mechanics (LEFM) are inapplicable for reasonably sized specimen due to extensive plasticity. In this paper, the multiple specimen resistance curve technique was employed for J-integral. The normal single side notched three-point bend (3PB) specimen was used to study the characteristic fracture parameter of high-density polyethylene pipe and its butt-fusion joints at different temperature. Testing results show that values of characteristic fracture parameter are affected by the welding process and experimental temperature respectively. The toughness value of HDPE butt-fusion joint is lowered than that of HDPE pipe. With the temperature decreasing, the toughness value of HDPE pipe and Butt-fusion welded joint decrease. And the same time testing results also show that J-integral can describe the fracture character of high-density polyethylene exactly. Testing results can be used for the engineering design and failure analysis of HDPE pipe.