A large number of structural, material, operational and environmental factors would have great influence on automotive brake squeal induced by friction, and the intrinsic influencing mechanism is a significant and challenging issue needs to be solved. Selecting a certain type of drum brake as the research object, a drum brake finite element model for frictional squeal is established using ABAQUS, a free-free modal test of individual brake components and the brake squeal bench test are performed to verify the model, and on the basis of which, the impact of Young’s modulus of shoes’ linings, brake pressure and friction coefficient on the squeal propensity is analyzed By introducing the contact pressure distribution properties between the drum and shoes, the intrinsic influencing mechanism of the factors above on squeal propensity is studied based on the complex eigenvalue theory. Results show that: (1) the squeal propensity of the drum brake decreases with the increase of Young’s Modulus of linings, while increases with the increase of friction coefficient and brake pressure; (2) the nonuniformity of contact pressure distribution is closely related to the squeal propensity and could make an unified explanation on the intrinsic influencing mechanism of the factors above; the squeal propensity decreases as the nonuniformity of contact pressure distribution increases, and the system tends to be more stable.