Nb 3 Sn is now recognized as the practical material for the high-field applications from 10 to 16 T, for particle accelerators, fusion and other related fields. However, the obtaining of high J c in Nb 3 Sn presently contradicts one of the most important stability criteria: to keep a small filament size, which makes the stability issue particularly prominent. Large filament sizes frequently cause flux jumps in the conductor, making quench detection and protection more challenging for Nb 3 Sn magnets. In this work, we try to numerically simulate the flux jumps more accurately down to a filamentary scale. Based on the theory of superconducting dynamics, we have established a theoretical model to describe the magnetothermal instability of Nb 3 Sn wires by considering the superconductor flux dynamics, heat diffusion and temperature response. The preliminary analysis of the test results for LPF3 which is a 16-T hybrid common coil dipole magnet fabricated by Institute of High Energy Physics is conducted to study the causes of its quenching and the impact of flux jumps on the magnet.