Intravenous injection is the most commonly used method for probe delivery in bio-imaging. While, the oral administration method might be more efficient than intravenous injection for fatty liver imaging due to the existence of liver “first pass effect”. However, this fundamental question has not yet been clarified. Meanwhile, in consideration of the deep tissue imaging and signal fidelity, fluorescent-photoacoustic (PA) dual-mode probes are much more desirable. Herein, an orally administrable dual-mode probe WSP-3 is revealed as a tool for imaging of the fatty liver disease and providing an insight into the above scientific question. A D-π-A system is linked with a rotatable C-C single bond in WSP-3, which facilitates the formation of a TICT state in low viscosity environments and an ICT state in high viscosity environments. Base on the positive correlation between fatty liver disease and cell viscosity, dual-mode imaging of non-alcoholic fatty liver disease (NAFLD) and drug-induced fatty liver disease (DIFLD) in vivo was accomplished. Moreover, control experiments indicated that the oral administration method demonstrated higher efficiency in fatty liver disease imaging, providing a fundamental reference for further probe-based fatty liver imaging.