In order to simulate the growth of plant stem, plant stem and branches were divided into fine grit, and the plant growth process was iterated by dividing the stem into tertiary structure of meristematic zone, elongation zone, maturation zone. The parametric L-systems theories were applied in simulating the geometry shape of the plant. This method can achieve a better result. For plant meristematic zone, three kinds of lateral bud factor of flower, subaxis, leaf were set to improve the controllability of different organs in plant growth. At last, the simulation experimental results showed that this method could reduce the complexity of parametric L-systems, and make the real simulation of plant’s growth process and the phenomena of botany.