Practical applications of fluid injection in environments with supercritical thermodynamic conditions and chemical composition are numerous, ranging from propulsion applications to manufacturing and drug delivery. Injecting the liquid into an environment where the temperature and pressure exceed its thermodynamic critical point is an important method that can significantly increase the efficiency of an engine. It is crucial to conduct in-depth research on the characteristics of interfacial phase behaviors in mixing process to illustrate the complicated nature of the sub/super/trans-critical jet. In this study, a novel pixelated-array masked phase-shifting interferometry platform is used to perform the visualization measurement accompanied with the mixing properties of the transcritical jet. The density field can be restructured by algorithmically processing interference images. The interfacial phase behaviors of various injection paths are studied and comparatively analysed. The results show that the interface behavior is dominated by turbulent mixing under transcritical jet which is a more efficient process than evaporation. A highly wrinkled continuous two-phase mixing layer exists at the interface of the jet, which gradually transitions from the liquid phase to the supercritical phase. The structure of the liquid jet in the supercritical environment consists of a liquid dense core, a two-phase mixing layer surrounding the liquid core, and an external low-density environment.