A fiber optic adapter assembly comprises an integrated main body with a housing part and an installation part, the housing part comprises a plurality of adapters in an integrally formed body, each adapter comprises an approaching opening, a front opening and a rear opening, the front opening and the rear opening are designed to receive an optical fiber connector and be matched with the optical fiber connector, and be optically connected with the optical fiber connector inserted into the front opening and the rear opening, an inner housing part and a sleeve ring for each adapter is aligned to a sleeve, the approaching opening is located between the front opening and the rear opening, and has a size allowing the aligning of the inner housing part and the sleeve ring to the sleeve to be positioned between the front opening and the rear opening in the adapter, the installation part is designed to mount the integrated main body in a casing by a front opening of the casing, and position thehousing part at the position near one side of the casing, and can approach the adapters by the front opening and the rear opening on the casing.