Globally, ecosystem functions are threatened by repeated droughts and declining plant diversity. Due to frequent droughts, the species in the plant community show different adaptions towards the extreme weather conditions. The aim of this report is to explore how the plant community changes over time. Considering the growth law of population, establish the model of precipitation and plant growth rate based on the Logistic function. Moreover, considering the competition and interaction between populations, this paper chooses the Lotka-Volterra model and adapt it, then use the improved Euler method to obtain numerical solutions of these nonlinear ordinary differential equations of plant population over time under the interaction of multiple populations. The observations are obtained: For the population of a plant community, when the rainy season intersects with droughts, the decline rate of the population at the inflection point slows down, the continuity of population change is interrupted. And the plant population shows an increasing trend in the rainy season, and a decreasing trend in droughts.