Fluorescence lifetime imaging microscopy (FLIM) has been widely used in biomedical research due to its high specificity, high sensitivity and quantification ability in cell microenvironment sensing. The fluorescence lifetime detection method based on time-correlated single photon counting (TCSPC) is one of the most commonly used techniques at present. However, due to the limitation of imaging principles and conditions, this technique has the disadvantages of long data acquisition time and consequently low imaging speed. In this paper, a fast FLIM technique for any number of discrete and irregular regions of interest (ROIs) in biological samples is developed. The technology uses acousto-optic deflectors (AODs) to achieve fast and flexible addressing scanning, optimize the synchronization strategy between AOD and TCSPC, and reconstruct the lifetime image through simple online feature analysis of the ROI shapes. For the case of multiple discrete irregular ROIs in biological samples, it can greatly save the time of data acquisition, thus realizing the fast FLIM imaging of these ROIs, which is benificial to the study of the heterogeneity of biological events in biological system. In particular, the fast fluorescence imaging result for 87 discrete points in the field of view shows that this method can obtain a fluorescence lifetime image in a very short acquisition time (only 52.2 ms) and thus achieving a very fast imaging speed in such a situation. Dynamic FLIM imaging of lysosome probe LysoSensor Green DND-189 in living cells stimulated by ammonium chloride is carried out to monitor the real-time change of pH value in lysosome lumen. The acquisition time for a single fluorescence lifetime image of lysosomes in two ROIs is only 200 ms. The results show that the rapid FLIM technology can be used to dynamically monitor the changes of microenvironment in biological samples, and will play an important role in the microenvironment sensing in living cells.