To evaluate the performance and optimize the structure of Love-wave surface acoustic wave（SAW）sensors in liquid-phase biosensing，we propose a bilayer waveguide structure of Au/SiO₂，with Cr used as the adhesion layer between SiO₂ and Au to improve the adhesion and density of SiO₂ deposited on Au. The feasibility of the Love-wave SAW bilayer waveguide structure was theoretically verified from the aspect of mass-loading sensitivity using finite element simulation software. The simulation results showed that the mass sensitivity reached the optimal value of−29.83 kHz·cm2/μg when Au=0.1 μm and SiO₂=2 μm. The thickness of Au=0.1 μm was consistent with the electrode thickness，and in subsequent experiments，the Au waveguide and electrode layers were fabricated together. In the experiment，a delay-line SAW device with a single Au waveguide layer on an ST-90°X quartz substrate was prepared using MEMS processes. The second waveguide layer of SiO₂ was deposited using PECVD，and aluminum films were grown in the delay line region as mass loads using thermal evaporation. The corrosion effect of the TMAH solution on the aluminum film was utilized，and a real-time detection system for the mass-loading sensitivity of SAW devices suitable for liquid-phase biosensors was employed to monitor the phase changes of the devices in real time，thereby verifying and evaluating the sensitivity of the bilayer waveguide SAW sensors. The results showed that the maximum phase change of the device was 124° when Au=0.1 μm，SiO₂=0.15 μm，and Al=0.15 μm. Under optimal parameters，by changing the thickness of the aluminum film，the sensitivity of the bilayer waveguide SAW sensor reached 0.81（°）/nm，demonstrating good linearity and stability.