The microstructure and mechanical behavior of solution treated Ti-41Nb alloy were systematically investigated by optical microscope, tensile test and in situ synchrotron high-energy X-ray diffraction. After solution treated at 800℃ plus water quenching, Ti-41Nb alloy presents a typical dual-phase structure which is characterized by exiguous lath-shaped α" martensite distributed on the equiaxed β matrix. The stress induced martensitic transformation (SIMT), together with elastic deformation, takes place concurrently during loading. The stress-induced martensitic transformation from β to α″ takes place intensively in the strain range from 0.0% to 3.3% but slightly from 3.3% to 4.0%. In the subsequent unloading process, the solution treated Ti-41Nb alloy undergoes elastic recovery, accompanied by the reverse martensitic transformation from α″ to β. After unloading, a large amount of α″ martensite has not been transformed into β parent phase, which results in a residual strain of 2.9%.