The sieve-pipette method is a traditional technique for determination of soil particle size distribution (PSD), while the laser diffraction method is a relatively new technology. To explore conversion relationship between the PSDs determined by the two different methods, 265 soil samples from 6 soil orders of the Chinese Soil Taxonomy were determined by the two methods. Results show that the clay content using the laser diffraction method was obviously lower than that using the sieve-pipette method, while the silt content using the former was higher than that using the latter, but the sand content was sometimes higher and sometimes lower with no consistent difference. However, significant relationships were found between the clay, silt and sand contents determined by the two different methods, even for each of the seven fractions of the USDA (United States Department of Agriculture) soil texture classification criteria. Based on the equations for conversion of data between the two methods, thresholds for classifying soil texture in clay, silt and sand were worked out, using the data obtained by the laser diffraction method. The findings demonstrate that data from the laser diffraction method can be directly used to classify soil texture.