To reduce the hygroscopicity of ammonium perchlorate(AP), the surface of AP was coated by polystyrene (PS) and fluorosilane(FAS: C₁₄F₁₂H₂₀SiO₃). AP/PS/FAS composite particles and AP/PS/FAS composite film were prepared via composite of AP and PS and processing of FAS. Their hygroscopicities were studied by moisture absorption rate and water contact angel test, and their micromorphology structures were investigated by scanning electron microscope-energy dispersive spectrometer (SEM-EDS) analysis. Results show that the moisture absorption rate of AP/PS/FAS film is the lowest, and it almost does not absorb moisture. The contact angel of untreated AP and AP/PS/FAS film with water are 0° and (113±2)°, respectively. The surface of AP/PS/FAS film is similar to the micromorphology structure of lotus leaf surface, and FAS molecules exsit in the surface of AP/PS/FAS film, it is advantageous to form hydrophobic surface.