In the long-term operation of the Chinese space station, a variety of in-orbit tasks are frequently conducted. A torque wrench has been proposed for extravehicular activities (EVA) by astronauts under microgravity conditions in space. This proposal introduces the structure and working principle of the wrench, conducting parameter design for key mechanisms, and performing strength verification for major load-bearing components. A prototype of the extravehicular wrench has been developed, and various tests have been conducted, including functional performance tests, environmental adaptability tests, and torque function durability tests. The test results show that the proposed EVA wrench has a simple mechanism and reliable motion, and can withstand large-scale vibrations and extreme temperature environments. It is suitable for use by astronauts during extravehicular activities.