The invention relates to an anchoring assembly of a mechanical packer for an oil field, particularly to a fully-enclosed track anchoring mechanism with the function of sand prevention. The fully-enclosed track anchoring mechanism comprises an upper connector, a track central pipe connected with the lower part of the upper connector and an anchoring assembly sleeving the track central pipe, wherein a switching pin is arranged at the inner end of the lower part of the anchoring assembly, and inserted into a track groove of the track central pipe; the lower end of the anchoring assembly is connected with a sand preventing sleeve; the track groove of the track central pipe is covered with the anchoring assembly and the sand preventing sleeve. The fully-enclosed track anchoring mechanism can well overcome the defects that the anchoring assembly and the track pipe have high possibility of being out of operation when foreign materials are clamped in the anchoring assembly and the track pipe; by being matched with a centering guide, the fully-enclosed track anchoring mechanism greatly improves working efficiency of underground operation, and reduces the manufacturing cost.