Abstract: The applications of Laser particle size analysis in sediment fields have been developed in recent years. Some factors such as the weight of the sample and dilution affect the measurement result of laser particle size analysis. For Micro S3500, the optimum weight of a sample is about 0.2 grams. If diluted, it affects the result of the particle size distribution. The method of sampling causes different random errors. Compared to the particle size distribution parameters (average size, standard deviation, skewness and kurtosis), the results obtained by laser analyzer show a smaller average size than the image method and sieving method. However, a good correlation for kurtosis was observed between the laser method and sieving method. According to the measurement results of 30 samples with two types of laser size analyzers of Micro S3500 and Malvern 2000, the average size obtained by Micro S3500 was bigger than that by Malvern 2000 with a good linear correlation (r=0.9574). In summary, results from the two analyzers provided a systemic difference in grain size. There are limitations and differences between every size analysis method. The particle size data should be obtained and analyzed by the same method in order to compare data from different references.