Many proteins undergo extensive posttranslational modifications (PTMs), such as methylation, acetylation, phosphorylation, glycosylation and ubiquitination. To elucidate the roles of these PTMs, it is necessary to generate homogeneously modified proteins. In this book, we are going to introduce the recently developed chemical synthetic methods for the synthesis of proteins with certain PTM(s). First, we introduce a ligation/S-alkylation approach for the semisynthesis N-terminal tail acetylated proteins. Next, we also introduce the dual native chemical ligation at lysine method for the synthesis of ubiquitinated peptides and proteins. Finally, we introduce a novel N-to-C sequential ligation method for protein total synthesis. These methods developed have dramatically promoted protein PTM research.