The present invention provides an in-situ regeneration method for a Ti-Si molecular sieve catalyst. The method comprises the steps of: (1) rinsing by a thermal solvent; (2) oxidation treatment by an oxidizing agent; and (3) washing by the thermal solvent. The thermal solvent in the step (1) is a basic thermal solvent with a pH value of 7-12, so as to remove organic matter that blocks a catalyst pore channel. In the step (2), at least one of a gas mixture of an oxidizing gas and an inert gas, or a hydrogen peroxide solution is used to perform the oxidation treatment on the catalyst, so as to remove the organic matter and oligomers attached on the catalyst and within the pore channel. In the step (3), the thermal solvent is used to wash the catalyst that has undergone the advanced oxidation treatment, so as to remove a residue of the advanced oxidation treatment. The method for regenerating the Ti-Si molecular sieve catalyst provided by the present invention has advantages of a short regeneration cycle, and a high activity recovery ratio of the regenerated catalyst.