<p>Controllably tuning the sensing performance of flexible mechanical sensors is important for them to realize on-demand sensing of various mechanical stimuli in different application scenarios. However, current regulating strategies focus on the construction process of individual sensors, the response performance of the as-formed sensors is still hard to autonomously tune with external stimulus changes like human skin. Here, we propose a new strategy that realizes post-tuning of the sensing performance by introducing a temperature-dependent phase transition elastomer into the sensing film. Through an interfacially confined photopolymerization reaction, a graphene-based phase-transition elastomeric (GPTE) film with a robust interface and excellent conductivity is well-formed at the water/air interface. Benefiting from the crystallization-melt dynamic switching in the elastomer network, the GPTE film could experience the reversible transformation between soft (1.65 MPa) and stiff (12.27 MPa) states, showing huge changes of elastic modulus up to seven times near the phase transition temperature (28.5 °C). Furthermore, the GPTE film is designed into a suspended perceptual configuration realizing the dynamic detection of 3D deformation adapted to temperature changes with up to 3.5-fold difference in response sensitivity. Finally, the self-adaptive sensing behavior of temperature-mediated 3D deformation is demonstrated by the effective detection of the dynamic stimulation process of cold and hot water droplets by the GPTE suspended film. The proposed strategy of phase transition-induced post-tuning of sensing performance could greatly facilitate flexible mechanical sensors towards a more intelligent one.</p>