The construction of grammars and the acquisition of syntactic structures from corpora are always considered as a time consuming task. Moreover, according to the purpose of the application, different standards have to be defined. In Machine Translation (MT), the situation is even more complicated since it covers two languages. In this paper, CSG-Tag, a Constraint based Synchronous Grammar (CSG) Tree Annotation System is proposed. This system provides a semi-automatic annotation process in the creation of syntactic structure of the source sentence linked with the corresponding target sentential patterns. All learned information are stored in Extensible Markup Language (XML) format and can be converted into grammar rules in application to MT. Moreover, the system has a function to import monolingual skeletal bracketing syntactic tree and Translation Corresponding Tree (TCT) structures in the creation of CSG rules. © 2011 IEEE.