A pile-bottom grouting cavity device, comprising: a grouting capsule , having an expansion state in which an interior of the grouting capsule is filled with grout to bear a pile body, and a contracted state in which an interior of the grouting capsule is hollow; a grouting pipe , communicated with an inner cavity of the grouting capsule for grouting the grouting capsule , and a fixing plate , provided with the grouting capsule thereon, and a through hole therethrough, wherein the through hole is to be communicated with a bottom of a accommodation hole for allowing slurry and/or sediment within the accommodation hole to pass through the through hole of the fixing plate , wherein the pile-bottom grouting cavity device further comprises a grout replenishing structure which communicates with the through hole for grouting into the through hole , wherein, the grout replenishing structure comprises at least one grout replenishing tube which is communicated with the through hole for grouting into the through hole ; characterized in that the fixing plate has a grout-storage chamber communicated with the through hole , and the grout replenishing tube is communicated with a grout inlet of the grout-storage chamber , wherein preferably, the grout replenishing tube has a second grouting portion extending into a cavity of the through hole and provided with a plurality of second grouting holes , and the second grouting portion is an arcuate tube extending along a hole wall contour of the through hole , more preferably, the second grouting portion is an annular pipe extending along the contour of the hole wall of the through hole . a grouting capsule , having an expansion state in which an interior of the grouting capsule is filled with grout to bear a pile body, and a contracted state in which an interior of the grouting capsule is hollow; a grouting pipe , communicated with an inner cavity of the grouting capsule for grouting the grouting capsule , and a fixing plate , provided with the grouting capsule thereon, and a through hole therethrough, wherein the through hole is to be communicated with a bottom of a accommodation hole for allowing slurry and/or sediment within the accommodation hole to pass through the through hole of the fixing plate , wherein the pile-bottom grouting cavity device further comprises a grout replenishing structure which communicates with the through hole for grouting into the through hole , wherein, the grout replenishing structure comprises at least one grout replenishing tube which is communicated with the through hole for grouting into the through hole ; characterized in that the fixing plate has a grout-storage chamber communicated with the through hole , and the grout replenishing tube is communicated with a grout inlet of the grout-storage chamber , wherein preferably, the grout replenishing tube has a second grouting portion extending into a cavity of the through hole and provided with a plurality of second grouting holes , and the second grouting portion is an arcuate tube extending along a hole wall contour of the through hole , more preferably, the second grouting portion is an annular pipe extending along the contour of the hole wall of the through hole . <EOS>