The present application relates to the field of immersed tube jointing, and more particularly relates to a post-grouting method for an immersed tube joint base. The post-grouting method includes the following steps: before locked backfilling of immersed tubes to be implanted, disposing a grouting tube capable of outputting solidifiable slurry in a furrow below immersed tubes; and after the locked backfilling, grouting the immersed tubes by using the grouting tube. For the purposes of adjusting postures and heights of the immersed tubes in case of abnormal settlement during installation, solving the problems on the stabilities and the service lives of immersed tube joints due to settlement of gravel mattresses or a geologic structure thereunder after installation, and enabling the immersed tubes to achieve a better bearing effect on a load during use, the present application provides the post-grouting method for the immersed tube joint base.