Grid-forming (GFM) inverter can enhance the system stability in weak grids, due to its ability to support grid voltage. However, under grid faults, GFM inverter systems still face transient stability problems. Compared with research on a single inverter system, the transient stability analysis of a paralleled system of GFM inverters can provide powerful support for understanding and optimizing the operation of multi-machine systems. In this paper, a Lyapunov energy function of a two-inverter system considering the damping effect is constructed. Subsequently, the transient analysis of the paralleled system is performed by estimating the stability region. In addition, a visualization method for a high-dimensional stability region is proposed to intuitively show the transient stability of paralleled inverter system, achieving a direct and accurate judgment of transient stability.