Abstract: Chinese giant solar telescope(CGST) is an on-axis Gregorian telescope, equipped with a 8 m diameter primary mirror and focal ratio of 1. The heat stop is a key component for the 8 m CGST, positioned at the primary focus, able to remove a heat load of 29 kW, while it absorbs a small portion of the heat at the same time. The geometry of the heat stop was designed, and four cases of sun-centered observations, limb observations, extreme coronal observations, out of range observations were emphatically simulated and analyzed with TracePro, calculating the irradiance distribution on elements of the heat stop, which provided data for the design of follow-up cooling system.