In order to effectively identify the fault type and locate the fault position in the large transformer, the micro-bionic fish is used for visual observation to inspect the internal transformer faults. The location of position and posture of miniature bionic fish is the key task in the process of detection. Aiming at the detection problem of position and posture of micro-bionic fish in metal enclosed space filled with transformer oil, a joint posture detection method based on acoustic-electric posture location and interial navigation is proposed in this study. Based on the analysis of the propagation characteristics of ultrasonic signals in transformer internal and shell, the installation mode of acoustic-electric position location device is put forward. Based on the embedded installation mode, the acoustic-electric positioning sensor is designed, the mathematical mode of transformer bionic fish posture calculation is constructed, and the simulation test of transformer bionic fish posture positioning is carried out. The test result shows that the simultaneous positioning of micro-bionic fish in transformer internal can be realized based on the acoustic-electric posture location and the calculation model of micro-bionic fish posture.