To reduce the complex optical path and circuit structure in optical dissolved oxygen concentration detection system, this paper proposes a methodology for detecting dissolved oxygen by frequency-domain fluorescence lifetime. The single-channel light source is used to detect the concentration of dissolved oxygen in water, which simplifies the optical path and circuit structure, improves the dissolved oxygen concentration detection algorithm and enhances the efficiency of inspection process. The effectiveness of the method is evaluated. Comparing with the results from an optical dissolved oxygen analyzer, our proposed method performed better in terms of the detection error (reduced from 0.1 mg/L to 0.04 mg/L in the range of 0~9 mg/L) and the stability (the standard deviation is decreased by 36% to 0.007 mg/L). Leveraging the implementation of a fast Fourier transform-based algorithm, the response time was reduced by an average of 12 seconds as steady state reached 90%, the response speed was increased to the percentage of 40% at the rise of concentration and 28% at the fall of concentration separately. The methodology demonstrated the effectiveness of detection accuracy, stability and response speed.