ABSTRACT OBJECTIVE：To investigate the quality differences of Pinelliae Rhizoma with different diameter，and to providereference for the rational utilization of its resources. METHODS：A total of 65 batches of commercial Pinelliae Rhizoma from thefour major medicinal markets in China and two companies were collected as samples，the diameter of them were measured byvernier caliper，and then them were screened into samples with different diameter ranges（0.5 cm≤d≤0.8 cm，0.8 cm＜d≤1.0cm，1.0 cm＜d≤1.2 cm，1.2 cm＜d≤1.5 cm，1.5 cm＜d≤2.0 cm）by sieving. The content of organic acids（oxalic acid，citricacid，L-malic acid，succinic acid，fumaric acid，trans-aconitic acid and cis-aconitic acid）in Pinelliae Rhizoma samples of differentdiameter ranges were determined by HPLC，and the content of the extracts of Pinelliae Rhizoma samples of different diameter ranges were determined by cold leaching method according to 2201 general principles in 2015 edition of Chinese Pharmacopoeia（Part Ⅳ），to evaluate the quality difference of Pinelliae Rhizoma in different diameter ranges.73 batches of Pinelliae Rhizoma fromcorresponding 10 main producing areas were collected as samples，to investigate its distribution of diameter. RESULTS：Dtermination of 65 batches of commercial Pinelliae Rhizoma showed that the content of organic acids and extracts in PinelliaeRhizoma increased with the increase of its diameter in general. However，there were no significant difference in organic acids andcontent of the extracts among Pinelliae Rhizoma samples of different diameter ranges in the same batch（P＞0.05）. The diameter distribution of 73 batches of Pinelliae Rhizoma from corresponding areas was mainly between 0.6 cm and 1.8 cm，with an averageweight of 95.54％. If the diameter standard（1-1.5 cm）specified in the 2015 edition of Chinese Pharmacopoeia（part Ⅰ）wasadopted，only 8 of 73 batches of Pinelliae Rhizoma meet the requirements，and the qualified rate was 10.96％；if the diameterrange was properly expanded to 0.7-1.5 cm，54 batches of Pinelliae Rhizoma meet the requirements，with a qualified rate of73.97％；when the diameter range was expanded to 0.7-1.6 cm，68 batches of Pinelliae Rhizoma meet the requirements，with aqualified rate of 93.15％ .CONCLUSIONS：There is no significant difference in the quality of Pinelliae Rhizoma with different diameters. Combined with the diameter distribution of Pinellia Rhizoma in different producing areas，the diameter range of 1-1.5cm specified in relative standard can be expanded to 0.7-1.6 cm，avoiding the waste of resources.