Liquid concentration detection is widely used in food, environment, biomedical and other fields. Based on the microwave method, a resonant coaxial probe liquid concentration detection device was studied, designed and realized. Firstly, ethanol-water solutions of different concentrations are selected as test samples, and the effects of coupling gap, probe immersion depth and probe conductor material on detection sensitivity are simulated and analyzed. To verify the feasibility of liquid concentration detection using the designed probe, ethanol-water solutions/glucose-water solutions with a volume concentration of 0~75%/ 0~50% are measured. The experimental results show that the probe is capable of accurately measuring the liquid concentration and the detection sensitivity in different concentration ranges can be optimized by adjusting the coupling gap. In addition, in this study, the quantitative inversion model of solution concentration is constructed by combining three electromagnetic parameters, namely, resonance frequency, S11 amplitude minima and quality factor. Compared with traditional method that only use resonance frequency as indicator, relative errors of liquid concentration of ethanol-water solutions/glucose-water solutions are suppressed from 5.79%/ 3.34% to 2.19%/ 1.36%, respectively. The probe is also able to effectively differentiate a variety of transparent liquids, such as ethanol solutions, glucose solution, salt water, tap water and deionized water, etc., showing good recognition ability and data reproducibility and thus shows a wide range of potential applications.