High sensitivity and a wide detection range are always the pursuit of sensor design. In this work, gold nanostars (Au NSs) featuring the shape of sea urchins with an absorption peak at the near infrared region (822 nm) were prepared. We proposed a Au NSs-based plasmonic colorimetric sensing platform for ultrasensitive catechol (CC) detection with a wide detection range from 3.33 nM to 107 μM and a limit of detection (LOD) at 1 nM. The target analyte, CC, was used to reduce silver ions (Ag+) to form silver (Ag) coating on the surface of Au NSs, which caused a blue-shift in the localized surface plasmon resonance (LSPR) of Au NSs. With the gradual increase in CC concentration, the Ag coating on the surface was gradually nucleated, and the LSPR blue-shift carried on. This strategy yields a wide LSPR shift by as much as 276 nm for plasmonic effects, enabling an ultra-wide range and the ultrasensitive detection of CC. This work will facilitate the research of target-mediated LSPR sensors and their wide application in environmental monitoring, food safety, and disease diagnosis.