The hazards of dust are receiving increasing attention with the application of bamboo industrialization. This study focuses on the morphological characteristics and formation mechanisms of milling dust from raw bamboo, dried bamboo, and thermally modified bamboo treated at varying temperatures. The particle size distribution, area-equivalent diameter, minimum Feret diameter, aspect ratio, roundness, and convexity were investigated. A new method combining sieving and image scanning analysis was applied to identify the size and morphology of the dust. The study has found that thermal modification significantly affects particle size and distribution, impacting dust convexity and surface characteristics. Particle size has a greater impact on dust morphology compared to heat treatment temperature. Thermal treatment is shown to degrade hemicellulose, reducing bamboo’s transverse mechanical properties and thereby altering the generated dust. The three-step cutting process is established, including bamboo milling deformation and dust formation by finite element simulation. This study offers a reference for optimizing dust removal ports and enabling real-time adjustments to dust removal system power based on dust morphology.