The effects of mischmetal hydride 0.5wt% addition on the graphite morphology according to the various S contents and holding times were investigated. The results obtained in this work were as follows. 1. Giving a short time after the MmH₂addition, nodular graphites were formed by means of many bubbles remained in the melt. 2. The more S was given in the melt, the less the surface tension of the melt became. So the remained gas bubbles in the case of high S Content were decreased both number and size, and irregular nodular graphites were formed. 3. Mischmetal sulfides remained in the melt acted as heterogeneous nuclei not for the graphite precipitation but for the gas bubble formation. The remained gas bubbles in the melt operated as the site of the graphite precipitation.