Abstract: Void is one of the most important factors which affects performances of composites. The void problem is generic to most polymer composite process, regardless of whether the matrix is a thermosetting or a thermoplastics matrix. In order to eliminate porosity and promote product quality, it is essential to study the bubble traversing behavior during composites manufacturing. Using the laminate simulation systems, the configuration changing process of bubbles under different traversing channels was investigated preliminarily. Then the main factors affecting bubble traversing behavior were studied respectively, such as the bubble volume, the resin viscosity and the inter-space size. Finally the kinematic conditions for bubble traversing were also proposed. The experimental results showed that the external pressure needed for bubble traversing in the woven layers would increase with the increase in resin viscosity, the decreasing of bubble diameter and the inter-space area. These results will provide experimental bases for the establishment of bubble movement model in hot-compaction process.