The invention discloses a steam channeling sealing method for a heavy oil thermal recovery horizontal well. The steam channeling sealing method comprises the following steps: (1) placing a steam injection pipe column into an oil layer portion, adopting a general injection manner, and injecting steam to preheat the formation; (2) injecting high viscosity jelly; (3) injecting a silicon salt high temperature plugging agent; (4) repeating the steps (2) and (3) until the construction design injection pressure requirement is reached; (5) injecting steam to heat the plugging agent, shutting and closing the well for 3-5d; and (6) injecting steam to perform huff and puff mining. The method realizes the integrated pipe string for sealing, steam injection and mining, the construction process is simple, and the operation cost is low; alternate injection of high and low viscosity systems can finally forms a high-residence and strong-sealing process, which effectively solves the formation channelingproblem of the low-viscosity and temperature-resistant sealing system, improves the residence of the plugging agent, expands the plugging volume of the temperature-resistant plugging agent, effectively blocks the steam channeling, expands a heating range of the steam injection, and improves the development effect of the heavy oil thermal recovery horizontal well.