Immune Evolutionary Algorithm (IEA) was a kind of evolution arithmetic based on Genetic Arithmetic (GA), which could strengthen the local search, and also considered the global search simultaneously. The present work took advantage of IEA to simulate the leaf area index (LAI) of strelitzia reginae, being one of the tropical plant. A satisfactory result was obtained that the average relative error was 3.44%. Therefore, this kind of simulation would probably give rise to some guiding signification for the planting and manage of Strelitzia reginae. IEA was an easy and simple method for the simulation of Strelitzia reginae LAI. Furthermore, it could also carve out a new way to establish the simulation model and parameter optimization of Strelitzia reginae LAI.