Fluorescence lifetime imaging is a rather effective and powerful method that can be used to analyze complex biological tissues and molecules. Conventional analyses of fluorescence lifetime data resolve the fluorescence decay profile in terms of discrete single exponential components with distinct lifetimes. In complex, heterogeneous biological samples such as tissue, multi-exponential decay functions can appear to provide a better fit to fluorescence decay data than the assumption of a single-exponential decay, but the assumption of multiple discrete components is essentially arbitrary. Quasi-Weibull distribution density function was likely to provide a truer representation of the underlying fluorescence dynamics. As comparing with those of single exponential and multi-exponential decay functions, the novel model can yield the better goodness of fit using data from multi-well plate assays of chemically and biologically interesting fluorophores. At the same time, the potential application of the quasi-Weibull distribution density function to fluorescence lifetime imaging was discussed.