The invention belongs to the technical field of a high-temperature gas cooled reactor nuclear fuel element production line and in particular relates to a thickening agent boiling device for a spherical nuclear fuel element production line and an application method thereof. The device comprises a feeding opening, a frequency conversion stirring speed reducer system, a groove body, a mechanical seal, a cold and hot water inlet, a cold and hot water outlet, a discharging opening, a special funnel for tetrahydrofurfuryl alcohol, an exhausting outlet and a groove body bracket. The equipment provided by the invention adopts a feeding valve bottom outlet design so that a bottom outlet can be effectively prevented from being blocked. By adopting the thickening agent boiling equipment provided by the invention, the difference of viscosity value of thickening agents in batches is relatively small and the product has relatively good uniformity. After trial, the present utilization condition is good.