PUFFIN is a lightweight block cipher, in which the block length is 64 bit while the key size is 128 bit. The integral cryptanalysis resistance ability of PUFFIN was analyzed. The existence of 5 and 6 round integral distinguisher in PUFFIN was constructed and proved. An integral attack on 8 round PUFFIN was mounted by 6 round integral distinguisher to recover 2 round 100 bit round cipher. The data complexity of the attack is 2²⁰ chosen plaintexts, the time complexity is about 2³³ 8 round encryptions, and the space complexity is 2²⁰. This has been the best integral attack on PUFFIN up to now.