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Ytterbium disilicate powders were synthesized by cocurrent chemical coprecipitation method. The in uence of Si/Yb molar ratio and calcination temperature on compositions and structures of Yb 2 Si 2 O 7 products were investigated. The formation mechanism and thermal behavior of precursor as well as the phase evolution of Yb 2 Si 2 O 7 were also discussed in depth. Results show that pure β-Yb 2 Si 2 O 7 powders with nanoscale size can be obtained from the precursor with Si/Yb molar ratio of 1.1 after being calcinated at temperatures above 1200 ℃. The Yb 2 Si 2 O 7 precursor is an amorphous polymer crosslinked with -[Si-O-Yb]-chain segments which are formed though Yb atoms embedding in the -[Si-O-Si]network. After a continuous dihydroxylation and structural ordering, the amorphous precursor transformed to α-Yb 2 Si 2 O 7 crystals by atomic rearrangement. Elevated calcination temperature can induce to the coordination structures and environment evolutions of structural units and then converted to stable (Si 2 O 7 ) groups and (YbO 6 ) polyhedrons, which results in the formation of β-Yb 2 Si 2 O 7 .