The invention discloses a gold nano probe for detecting benzoyl peroxide as well as a preparation method and application thereof. The nano probe is a gold nano-particle assembly with a "core-satellite" structure, gold nano-particles carried with boric acid group compounds in a decorated mode serve as the "core" (C-AuNPs), gold nano-particles with compounds which can react with boric acid groups to form boric acid esters in a decorated mode serve as the "satellite" (S-AuNPs), and the gold nano-particles serving as the "core" and the gold nano-particles serving as the "satellite" are connected by forming boric acid ester groups. The nano probe can be used for nano-mole-level BPO colorimetric detection under the condition that no complex instrument exists, the detection speed is high, the accuracy is good, and the sensitivity is high; under the condition that the specific concentration of the BPO does not need to be known, according to the color change, whether the BPO is contained in a sample or not and the general content range can be judged in a qualitative/semi-quantitative mode, and whether the content of the BPO in the sample exceeds the standard or not can be judged.