This article presents the development of a 2D model for HTSMA which focus on interfaces motion in the martensitic state. We consider the topology of a 2D representative “volume” constituted of 4 martensite variants. Interfacial force is derived using Eshelby’s energy momentum tensor ans compared with a critical threshold which depends on interfacial lenght. A criterion for annihiling compatible interfaces is incorporated in this framework. The model is firtly applied to the description of detwinning mechanism in a grain. First results are presented.