Abstract: In response to the frequent occurrence of oil pipeline theft cases in recent years and the difficulty in implementing routine detection of theft orifices during actual pipeline maintenance, this paper introduced the detection principles, system architecture, and implementation procedures of triaxial composite specialized in-line inspection. Through field engineering applications, the study combined triaxial spatial magnetic field signals with eddy current signals to interpret and identify characteristic signals of theft orifices. Results demonstrated that triaxial spatial magnetic field signals exhibited high sensitivity to external wall information of pipelines, while eddy current signals primarily responded to internal wall characteristics due to skin effect influences. By applying the principle of characteristic signal consistency for theft orifices, combined with signal features and theft methodologies, the system effectively identified pipeline theft orifice signals, avoiding misjudgment and missed detection. This research provided technical support for establishing standardized detection procedures, data analysis, and signal recognition protocols for routine oil pipeline theft orifice inspection in the future.