Deformation-induced microstructure evolution of Polyamide 1012 and its alloys with PA612, with an emphasis on lamella development, polymorphism transition and molecular orientation, is investigated in this work. When the materials was deformed above Tg of PA1012, a series of complex SAXS patterns are continuously identified at intermediate strain including four points, a figure-eight and an X-shaped pattern, accompanied with two-bars pattern on the meridian, which corresponds to the transient microstructure. Such particular structure is resulted from the approach of tilted lamellae along the drawing direction, the insertion and the orientation of new lamellae. To investigate the temperature dependence, the microstructure developments at different temperature, which was below, above, or close to Tg, are compared. Based on the comprehensive results, the correlation between microstructure and mechanical response has been successfully established, which is featured by the synchronous occurrence of transient structure with slight strain hardening.