With the development of the petrochemical industry, pipeline inspection technology plays a vital role in terms of avoiding explosions and protecting people's life and property. Pipelines working in high-temperature environments suffer from dual dangers of internal and external wall defects. It is often difficult to find a single nondestructive testing (NDT) method that can cover internal and external defects detection especially in high-temperature environments. In order to discover pipeline defects in time, we propose a hybrid online monitoring method for comprehensive defects inspection in high-temperature environments. This hybrid monitoring method combines eddy current testing (ECT) with electromagnetic acoustic transducer (EMAT) techniques. Specifically, we split the coil signal into two channels; one channel gives ECT signal and the other gives EMAT signal; furthermore, we demonstrate the feasibility of the proposed hybrid monitoring method by numerical simulations and laboratory experiments. The results show that the proposed hybrid online monitoring method can be used successfully to simultaneously monitor surface and internal defects and has high stability even at temperatures above 300 °C. Our approach achieves the genuine integration of ECT/EMAT technologies, effectively addressing the challenge of incomplete monitoring of pipeline defects in high-temperature environments.