In this study, to evaluate the influence of grid blast following to the peening process on the fatigue strength improvement, residual stress measurement and fatigue tests have been conducted. Examined peening processes were UIT, PPP and HP with ICR apparatus. For the residual stress measurement, plate and on-bead specimens made of JIS-SM400, SBHS400, SBHS500 and SBHS700 were used, and X-ray diffraction method was applied to the measurement. The results concluded that the differences in the compressive residual stress distribution in the vicinity of peened area with and without blast are not so significant. For the fatigue tests, out-of-plane gusset welded joint specimens made of JIS-SM490 and SBHS500 were used. Fatigue tests were conducted under stress ratio R=0.0 and 0.5. Fatigue tests showed that fatigue strength of peened specimens with blast are almost the same as that of peened specimens without blast, and those results were observed independently of steel grade and of peening methods.