<p><i>Dreissena polymorpha</i>, an invasive species in North America, poses a serious threat to the environment and economy. It suffocates native species and clogs infrastructure, disrupting ecosystems. Since this species can also indicate biological pollution in water bodies, early monitoring can enable effective intervention and control measures to mitigate ecological and economic losses. Herein, a strategy was constructed for <i>Dreissena polymorpha</i> DNA detection with enzyme-assisted target recovery coupling DNAzyme-driven double-cycle signal amplification. This detection method utilizes the signal transduction mode of commercial pregnancy test strips. Magnetic beads conjugated with H1 (MB-H1) are hybridized to human chorionic gonadotropin-coupled H2 (hCG-H2). Target binding triggers toehold-mediated strand displacement. The cleavage of the endonuclease releases the target and hCG-H2 and generates DNAzyme. The DNAzyme, activated by Mn²⁺, cleaves MB-ssDNA-hCG substrate, releasing abundant free hCG. This converts the target into free hCG, detected visually via commercial pregnancy test strips. The test strip assay showed high sensitivity with a limit of detection of 3.3 fM and showed great potential for monitoring invasive species in a portable and device-free manner, providing practical advantages for ecological management. This use of existing immediate equipment to enable portable detection of non-primary targets demonstrates high potential and advantage.</p> Graphical Abstract <p></p>