A 3-D model with specific parameters was established, utilizing the conjugate heat transfer method to calculate heat exchange between the rock and fluid, and the smoothed particle hydrodynamics-finite element method approach to simulate rock fragmentation. Upon contact, the liquid nitrogen jet induced significant heat exchange, with the 25 MPa jet showing larger contact area and higher efficiency. Notably, the impact center of the 400°C rock exhibited a slight temperature rise due to energy release. Liquid nitrogen reduced the rock's tensile, compressive strengths, and elastic modulus. High temperature rocks (400°C) had a 15.8% higher eroded volume fraction than those at 200°C. Increasing jet pressure from 20-25 MPa resulted in a 32.0% erosion increase. Additionally, a decrease in elastic modulus for 200°C granite led to a 19.9% increase in erosion.