Shrinkage formation often causes fatal defects in castings. Recently, the development of computer technology has provided us with a useful and effective method to predict shrinkage formation. A particle method is a Lagrangian method that uses discrete objects as calculation elements which is referred to as particles, and they can move freely in the space. Therefore, this method can calculate shrinkage formation directly. In this study, solidification simulation and flow simulation programs based on the particle method were combined considering the temperature-dependency of density. The program was applied to the solidification problem of a cylindrical pure Sn casting, and the predicted shrinkage was compared with experimental results. First, the calculation stability for a still fluid was discussed and an improved method was proposed. The flow of a fluid during solidification is quite slow; however, the particle method has a fundamental difficulty in calculating slow flow phenomena. Therefore, creep flow was assumed. When the inertia force was not considered, the calculation stability improved significantly, and introduction of a gravity adjustment coefficient reduced calculation time significantly. Next, the proposed method was applied to shrinkage formation analysis with an influence of air-cooling. As a result, predicted shrinkage shape agreed well with experimental result. [doi:10.2320/matertrans.M2011186]