Real-time detection of aerosol flow field using planar laser-induced fluorescence (PLIF) technology is crucial for studying the motion of aerosol. To enhance the visibility of weak signals in real-time PLIF aerosol signal detection, we propose a method of piecewise intensity transformation in this paper. This method sets constraints based on the characteristics of signal intensity, iteratively divides the signal into several intensity ranges, and then replans the signal intensity in each range. The proposed piecewise intensity transformation is applied to the signal processing of PLIF aerosol flow field detection,compared with the processing results of limited contrast adaptive histogram equalization (CLAHE), this method has good results in weak signal enhancement and noise suppression of large dynamic range fluorescent signals, with an improvement of over 20% in the signal-to-background ratio of weak signals. The proposed method achieves real-time detection at 25 frames per second for different stages of aerosol flow field, meeting the requirements for real-time detection of aerosol flow field fluorescence signal.