Si-N-O films have drawn researcher’s much attention recently due to their potential superiority in blood compatibility of biomaterials. In this paper, Si-N-O films were synthesized on <100> silicon substrates by pulsed reactive unbalanced magnetron sputtering a single crystal silicon target with high purity in a mixture atmosphere of Ar and N2. XPS and FTIR results showed the Si-N-O films synthesized at higher N2 flux could be described to random bonding model (RBM). In RBM, the Si2p existed in the form of a-Si3N4 and SiNνO4-ν (ν=0,1,2,3,4) components. Platelet adhesion behavior on Si-N-O films was assessed by platelet adhesion test and Lactate dehydrogenase (LDH) assay, qualitatively and quantitatively separately. The correlativity of film chemical structure and blood compatibility was investigated. The results of platelet adhesion and activation showed that the RBM film with higher N/O ratio exhibited favorable blood compatibility. It was shown that the Si-N-O film with specific composition and chemical bonding state was superior in blood compatibility compared to low temperature isotropic carbon (LTIC).