The invention relates to a fixture device of a deepwater floating platform rib anchor chain sensor. The device is characterized by comprising a T-shaped fixture body, self-locking devices and a sensor bearing cylinder; three ends of the T-shaped fixture body are respectively provided with one self-locking device; and the sensor bearing cylinder is horizontally fixed on the wing plate of the T-shaped fixture body. The device disclosed by the invention is not only used for effectively preventing the installed sensor from sliding along a chain ring but also used for preventing the sensor from rotating relative to the chain ring and ensuring the good in-place working state of the sensor. Simultaneously, a diver serves as an installation carrier; the diver can sufficiently play subjective initiative; more complex works can be completed; and installation risks resulted from reasons, such as improper operation, ocean current disturbance and the like, can be reduced.