In this study, data of Uroteuthis edulis were collected from the catch of torch-light net, pole and line boote and trawl net, and scientific surveys as well. Determination of potential spawning ground was based on the dorsal mental length and maturity stage frequencies distribution. From May to Nov. 2009, 4000 samples were collected. For the catch of torch-light net from May to Nov., most mature individuals occurred in western waters off Peng-Jia islet. The percentage of mature individuals was a bit lower in the waters off northern Taiwan and lowest in the northeastern waters off Peng-Jia islet. For the catch of trawl net in Aug. and Sep. 2009, the pattern was identical to the result of torch-light net, mature individuals occurred in the western waters off Peng-Jia islet and immature ones occurred mostly in the northeastern waters Peng-Jia islet. While in Nov. 2009, all squids caught in the northern waters off Peng-Jia islet were fully mature. For pole and lines, a majority of mature squids were found with 15 miles west of Peng-Jia islet. Judging from the catch for all fishing methods combined, the northwestern waters off Peng-Jia islet is a potential spawning ground for U. edulis.