The invention provides a high-pressure jet grouting and shallow-layer stirring combination in-situ remediation method for soil and underground water and belongs to the technical field of soil and underground water in-situ remediation methods. The combination in-situ remediation method comprises the following steps: distributing high-pressure jet grouting in-situ injection points, and carrying out measurement, locating and pre-boring; carrying out the high-pressure jet grouting injection of a deep layer in one to three times; carrying out the in-situ stirring of a shallow layer in one to two times; carrying out agent reaction and underground water monitoring; and carrying out self-inspection and acceptance. Agents which are injected for high-pressure jet grouting injection in three times are sequentially C+N1+N2, K and K+B. Agents which are added for the in-situ stirring of the shallow layer are C+F+N1+N2. The highest adding ratio of part of the high-pressure jet grouting injection of the deep-layer zone is as follows: the agent C accounts for 1.6-2.4%, and the agent K accounts for 1-5.4%. Being used as the remediation solution of an organic pollution engineering with sporadic pollution spots in part of severe soil and underground water plots, the remediation method has the advantages of being short in construction period, being great in effect and being capable of adapting to various strata and is used as an important technical means for replenishing remediation.