Smart theranostics agents triggered by endogenous H2 S with combined activated photoacoustic imaging and photothermal therapy can improve the diagnosis and treatment of colon cancer. However, the low theranostic performance of the current smart theranostics agents after the triggering step has limited their further application. In this work, the theranostic performance of endogenous H2 S-triggered Au@Cu2 O for the diagnosis and treatment of colon cancer, which is generated from the localized surface plasmon resonance coupling effect between a noble metal (Au) and a semiconductor (Cu2 O), is investigated. Compared with Cu2 O, the prepared H2 S-triggered Au@Cu2 O shows a significantly stronger absorption at the near-infrared region, such as a ≈2.1 times change at 808 nm, giving a photothermal conversion efficiency increase of ≈1.2 times. More importantly, Au@Cu2 O still exhibits good photoacoustic imaging contrast and photothermal properties for treatment of colon cancer in vivo even at very low injection doses. This work not only investigates an endogenous H2 S-triggered Au@Cu2 O theranostic agent with enhanced theranostic performance for colon cancer but also provides a novel strategy for designing high-performance theranostic agents.