The braking torque of the carbon ceramic braking system of the landing gear increases with the reduction of wheel speed under the condition of rapid change of angular speed. The negative slope of the braking torque and wheel speed curve has a great re? lationship with the landing gear walking vibration. Focusing on the impact of the negative slope of the braking torque on the landing gear brake vibration， a three degree of freedom landing gear brake walking model is established， and the main landing gear brake vi? bration of amphibious aircraft is analyzed. The calculated acceleration response and frequency are consistent with the test results of the landing gear field skid brake test. The effects of initial braking torque， negative slope， landing gear heading stiffness and damp? ing， strut equivalent height and other parameters on the landing gear dynamic system are studied， and the dual parameter vibration convergence boundary of initial braking torque and negative slope of braking torque under high speed braking is given. By means of Hopper bifurcation analysis， the two parameter stability boundary of the negative slope of braking torque and velocity under the global state of the landing gear system is given. Through analysis， it is concluded that the gear walk may be caused by two reasons： the negative slope of the braking torque exceeds a certain range， or the braking torque is too large due to large braking pressure， and the slip ratio exceeds the limit. Compared with high speed braking， the negative slope of braking torque has greater influence on the stability of low speed braking. Finally， based on the analysis results， the methods and suggestions to improve the gear walk? ing vibration of landing gear are given.