Endogenous carbon monoxide (CO) is mainly produced from degraded heme due to HO-1 expression, which is a pivotal part in vasodilation and neurotransmission, anti-inflammatory and anti-apoptotic processes. Due to the significant protective role of CO in vivo, the real-time monitoring of endogenous CO is of particular importance. However, when detecting CO in vivo, the catalysis of heavy metal ions has usually been required in previous reports, which would restrict the bio-applications of the CO probe. To overcome this difficulty, herein, a turn-on silicone fluorescence probe (SAH-N) has been rationally designed, which does not require the catalytic effect of metal ions in the CO reduction process. SAH-N shows superior concentration and time dependence in hypoxia. Moreover, SAH-N excels in sensitivity, selectivity and stability, and succeeds in visualizing the presence of CO in zebrafish. We expect that the silicone fluorescent probe SAN-H will further contribute to in situ CO detection in biological systems.