An absorbable PEG-based hydrogel prepared from a multi-arm-PEG-vinylsulfone having about 3 to about 8 arms and a multi-arm-PEG-R-sulfhydryl having about 3 to about 8 arms; where R is defined as an ester linkage, such as carboxylate ester, lactate ester, and isobutyrate ester have been disclosed. Additionally, sustained release compositions that are prepared from an absorbable PEG-based hydrogel and a protein have been disclosed which provide sustained release of proteins and peptides.