High-pressure Raman studies have been carried out on single crystalline C-60(Fc)(2) nanosheets up to 254 GPa. Our results show that the charge transfer between Fc (ferrocene) and C-60 increases in the low-pressure range. Above 5 GPa, C-60 molecules start to form a chainlike polymer structure, and this polymerization is reversible upon decompression, in contrast to that of pristine C-60. The special layered structure of C-60(Fc)2 restricts the polymerization of C-60 molecules in some directions and explains the formation of the linear chainlike polymeric structure of the C-60 lattice under pressure. We suggest that the reversible polymerization is related to the increased charge transfer and the overridden steric repulsion of counterions.