Complex multi-area collaborative coverage path planning in dynamic environments poses a significant challenge for multi-fixed-wing UAVs(multi-UAV). This study establishes a comprehensive framework that incorporates UAV capabilities, terrain, complex areas, and mission dynamics. A novel dynamic collaborative path planning algorithm is introduced, designed to ensure complete coverage of designated areas. This algorithm meticulously optimizes the operation, entry, and transition paths for each UAV,while also establishing evaluation metrics to refine coverage sequences for each area. Additionally, a three-dimensional path is computed utilizing an altitude descent method, effectively integrating twodimensional coverage paths with altitude constraints. The efficacy of the proposed approach is validated through digital simulations and mixed-reality semi-physical experiments across a variety of dynamic scenarios, including both single-area and multi-area coverage by multi-UAV. Results show that the coverage paths generated by this method significantly reduce both computation time and path length,providing a reliable solution for dynamic multi-UAV mission planning in semi-physical environments.