•The expansion characteristics of PASJ were explored.•The movement behavior of abrasive particles in PASJ was analyzed.•The flow characteristics of the shear layer in PASJ were investigated.•The periodic characteristics of PASJ were demonstrated. Supercritical carbon dioxide (SC-CO2) jet has a wide range of applications for rock-breaking and fracturing in oil-gas exploration and development due to its special physical properties. Pulsed abrasive SC-CO2 jet (PASJ) created by self-excited oscillation has excellent rock-breaking performance, but its flow characteristics are still unidentified. Hence, the expansion characteristics of the jet, the motion behavior of the abrasive particles, the flow characteristics of the shear layer vortex ring, and the periodic characteristics of the jet were experimentally investigated by high-speed photography in this study. The results show that both the fluid expansion angle θf and abrasive particles expansion angle θp are affected by the nozzle structure and working parameters, while the latter is irrelevant to the length of the nozzle cavity. The tangent of fluid expansion angle θf at supercritical and subcritical environments are in the range of 0.24–0.34 and 0.15–0.27, respectively, while the tangent of abrasive particles expansion angle θp is between 0.22 and 0.3. Furthermore, the process of vortex ring extension, stretching, flipping, folding back, and collapse can be observed at the fluid boundary of the jet. Besides, at the supercritical ambient pressure, the position of the abrasive particles in the jet affects the line grayness variation, while in the subcritical ambient pressure, the line grayness variation is mainly influenced by the phase change of CO2 and the shear layer vortex ring evolution. The clarification of the flow characteristics of PASJ in this study can help promote its rock breaking performance for underground energy exploration.