The traditional detection methods of substance concentration are mainly based on absorption spectrophotometry, including spectrophotometer, gas phase or liquid chromatography, etc. Although these methods have high sensitivity, due to the complex testing process, testing equipment is too large and time-consuming. Therefore, a convenient method for measuring small changes in refractive index of solution is investigated. We mainly use the high order model of the double-sided metal clad waveguide to achieve the high sensitivity of measurement. We proposed a bimetallic clad waveguide structure, the sample to be tested was used as its guide layer, and two metal films were used as its cladding layer. A tiny change of extinction coeffient in the waveguide guiding layer where the acetic acid solution and bromocresol green can lead to a significant change of light intensity in the reflection spectrum. Trace detection of substances was achieved by using the Attenuated Total Reflection curves of the double-sided metal-clad waveguides in response to the waveguides structure. Both theoretical simulation and experimental results showed that using this method, the detection limit of acetic acid can be as low as 1.3 nm, which was 16 times higher than the surface plasma field enhanced resonance scattering (SP-RLS) method, and four times higher than flame atomic absorption spectrometry and fluorescence spectrometry, respectively. This method is a real-time detection technology of solution concentration which is short in time, requires less samples, has high stability, is convenient and cheap, and provides an effective detection route for the chemical production process in the future.