Abstract: A new tracer particle relaxation modeling was presented to evaluate the PIV particle tracking ability, which improved the applicability of relaxation modeling as normal Mach number more than 1.4. Applying the new modeling to PIV experiment, the PIV system and tracer particle seeding technology were developed, and PIV quantificational measurement ability was demonstrated. The numerical simulation of tracking and dispersion characteristics of tracer particles in 2D spatial development supersonic gas-solid two-phase mixing layer was investigated with different Stokes numbers and convective Mach numbers. The smaller tracer particle diameters show the better tracking characteristics for the same convective Mach number flow. The particles present the largest dispersion distance as the Stokes number between 1 and 10. Particle distribution characteristics in mixing coherent vortex structure are represented by the diameters. With the decrease of the particle scale, the particles mixing with the gas vortex are strengthened. The particle tracking characteristics turn worse as the convective Mach number increases for the same tracking particle diameter.