Accurate quantification of proprotein convertase subtilisin/kexin type 9 (PCSK9) in serum before and after the medication is helpful in grasping the evolution of PCSK9-related disease and evaluating the efficacy of PCSK9 inhibitors. Conventional approaches for PCSK9 quantification suffered from complicated operations and low sensitivity. By integrating stimuli-responsive mesoporous silica nanoparticles, dual-recognition proximity hybridization, and T7 exonuclease-assisted recycling amplification, a novel homogeneous chemiluminescence (CL) imaging approach was proposed for ultrasensitive and convenient immunoassay of PCSK9. Owing to the intelligent design and signal amplification property, the whole assay was conducted without separation and rinsing, significantly simplifying the procedure and eliminating the errors associated with the professional operation; meanwhile, it showed linear ranges over 5 orders of magnitude and detection limit as low as 0.7 pg mL–1. Parallel testing was allowed due to the imaging readout, which brought a maximum throughput of 26 tests h–1. The proposed CL approach was applied to analyze PCSK9 from hyperlipidemia mice before and after the intervention of the PCSK9 inhibitor. Serum PCSK9 levels in the model group and the intervention group could be distinguished efficiently. The results were reliable compared to commercial immunoassay results and histopathologic findings. Thus, it could facilitate the monitoring of the serum PCSK9 level and the lipid-lowering effect of the PCSK9 inhibitor, showing promising potential in bioanalysis and pharmaceuticals.