Well-developed repent stems grown on Pooideae, when it is growing, the new unit will also grow on their nodes, the two growing process is parallel. To research the parallel growth process in the coordinate system, we collected much growth data, observed and studied them, then put forward the parallel growth model based on state-space, the model can reflect parallel growing of repent stem continually and dynamically, and it is also easily to understand. It provide a new research method for visual plant modeling.