The invention relates to a bottom adding device and bottom adding method for in-situ soil removal. The bottom adding device comprises a base and a soil box body transfer device, wherein the base comprises a bottom plate fixing part, a shovel head storage part and a box body transfer device body fixing part, wherein the bottom plate fixing part, the shovel head storage part and the box body transfer device body fixing part are sequentially connected; the soil box body transfer device comprises a body part and a shovel head, wherein the body part comprises a seat body and an ejection module; anejection head of the ejection module is arranged behind the shovel head and is used for ejecting the soil box body on the shovel head when being driven; a fixing part of the ejection module is arranged on the seat body; the seat body of the body part is provided with a positioning block; a positioning groove is formed in the box body transfer device body fixing part of the base and is used for positioning and supporting the positioning block; the shovel head storage part is provided with a rail frame; the shovel head is placed on the rail frame during bottom adding; and the bottom plate fixingpart is provided with a bottom plate support and an edge stop. The bottom adding device and the bottom adding method can effectively pack soil blocks so as to ensure the integrity of the soil blocksin the transfer process.