This paper concern with analyze statistically the sediment grain size distribution of the Nakdong River delta, which formed interdistributary island (upper delta) and barrier islands (lower delta). Various factors related to grain-size distribution, such as the shape of cumulative curves, frequency curves and histogram and various other parameters calculated from grain-size distribution have been tried as environmental indicators. The results of this study are as follows: (1)The mean grain size of interdistributary islands are finer than barrier islands, i.e. Shinheung-Ri is 3.29, Ulsug-Do is 3.09, Sae-Deung is 1.53 Paghap-Deung is 2.44 and Namusit-Deung is 2.45. The mean size of deposits becoming rather coarser and coarser as toward the down stream. (2) The standard deviations are 1.5 in Shinheung-Ri, 1.2 in Ulsug-Do, 0.43 in Sae-Deung, 0.35 in Paghap-Deung and 0.38 in Namusit-Deung. The sorting of average depends upon the distance of transport, in this case sorting coefficient becoming better and better as toward the lower delta. (3) Interdistributary islands and barrier islands represented positive skewness except Sae-Deung one of barrier islands. Generally, skewness has near-zero value in all over the study area. (4) On the shapes of histograms for grain sizes distribution have single peak pattern. The peaks of histograms are located on 3~ and become concentrated intensively toward the barrir islands. It represented homogeneity of deposits grain size especially in barrier islands. (5) The characteristics of CM diagram represents predominant mechanism in each islands such as rolling and suspension in upper delta, turbidity in Sae-Deung, suspension or saltation in Namusit-Deung and Paghap-Deung. (6) In the cumulative grain-size distribution curves on normal probability paper, have 4 straight segments in upper delta, and have 3 straight segments in barrier islands. The main transportation mechanism of deposits are saltation in Shinheung-Ri, saltation and suspension in Ulsug-Do and saltation mechanism in barrier islands. The results of CM diagram which represented the transportation mechanixrn of deposits shows not same as the results of normal probability paper representation. (7) On the scatter diagram of standard deviation and skewness, in the case of Shinheung-Ri, there is a tendency to indicate that the better sorting the higher value of negative skewness. In the case of the Ulsug-Do, on the other hand, the opposite tendency is found. In the case of barrier islands can not find the interrelation between each other. On the scatter diagram of standard deviation and M~ seems to also there is not any interrelation between each other.