Femtosecond laser molecular tagging velocimetry technology is the most commonly used non-invasive velocity measurement method. Traditional nitrogen-based molecular tagging velocimetry has a weak signal, a poor signal-to-noise ratio, and a small dynamic range of velocity measurement, which limits its application, especially in low-speed flow field. This paper mainly researches the femtosecond laser-induced chemiluminescence velocimetry technology. Femtosecond laser is introduced to interact with methane/nitrogen flow field, and generate a cyano fluorescence with strong signal intensity and long luminous duration, thus achieving a high signal-to-noise ratio, high precision and wide range velocity measurement. The experimental results show that by changing the concentration of methane, we can adjust the intensity and duration of the cyano fluorescence signal. The lower the concentration, the longer the cyano fluorescence signal lasts. In velocity measurement, it is necessary to comprehensively consider the fluorescence intensity and fluorescence duration required for velocity measurement, and select the appropriate methane concentration to achieve the best velocity measurement effect. This paper also explores the range of the velocity measurement of this method. The method has no upper limit, but the actual measurement upper limit is mainly affected by the time resolution of the hardware of the delay triggering device, the spatial resolution of the imaging system and the minimum gate width of the camera. There is a lower limit of this method. At a concentration of 500 ppm, the fluorescence signal intensity with a signal-to-noise ratio of 8 can still be obtained at 120 μs after the laser radiation. The minimum resolvable displacement of the imaging system in this experiment is 27 μm, and the lower limit under this experimental condition is 0.23 m/s. A lower limit can be obtained by further reducing the methane concentration. In addition, the influence of the laser energy and delay time on the speed measurement accuracy was evaluated through experiments. This work has greatly expanded the application range of femtosecond laser molecular tagging velocimetry, and has great application potential in the field of aerospace.