This document specifies the terms and definitions, method principles, general requirements, testing equipment, testing steps, data processing, testing results and evaluation, testing records and testing reports for terahertz non-destructive testing of the bonded interface of mullite fiber composite materials. This document is suitable for terahertz non-destructive testing of the bonding interface of mullite fiber composite materials. Terahertz time domain spectroscopy testing of the bonding interface of multi-bonding structures of other non-metallic materials can also be used as a reference.