The effect of testing temperature on retained austenite (RA) stability of industrially cold rolled CMnSi sheet steel treated by quenching and partitioning (Q&P) process has been investigated by observing the deformation and transformation behavior of RA at different testing temperatures. Uniaxial tensile properties at different temperatures were determined and a correlation between RA stability and mechanical properties were also established. Ultimate tensile strength increases monotonously when temperature decreases, while total elongation reaches an optimum value between 0 and 20°C, where RA exhibits the greatest TRIP effect. Work hardening rate was calculated to decrease through three different stages in an oscillation manner, leading to significant enhancement in both strength and ductility. The kinetic of deformation-induced martensite transformation is also studied and the stability of RA can be evaluated by comparing the kinetic parameter β.