Chandox 3-jaw hollow power chuck fixture includes a built-in type cylinder, suitable for machining application on working table. It is rust-proof for pneumatic cylinder. The inside wall of the cylinder is rustproof treated. The cylinder can work under wet or high moisture circumstances without rusty or seized trouble. Its dust-proof and water-proof structure prevents work-chips and coolant water from entering into inside of chuck cylinder to maintain its accuracy and lead to longer service life. The cylinder is connected directly to a chuck for obtaining better stability, less space and higher machining efficiency.