Patterned fine particles enable a lot of applications. Hydrophobic/hydrophilic patterning with groove on a substrate is effective in site-selective dip coating in which suspension including particles spreads on desired area and then particles assemble with the evaporation of solvent. This paper aims to construct a model of the self-assembly process including the conditions of assembly start or not on such substrate. We investigated the height and shape of suspension spreading over hydrophilic/hydrophobic patterned groove. In addition, critical local contact angle which determines the self-assembly will start or not was modeled. In order to verify this hypothesis, we examined both effects of change in contact angle on hydrophobic region and groove depth on the particles assembly. It was found that the width can be estimated based on the local contact angle of the spreading profile.