With the rapid development of high-throughput sequencing and its wide application in viroid research,more viroids or viroid-like circular RNA molecules were identified from different organisms,posing a new challenge to viroid taxonomy and demarcation.Viroid study group modified the rules of viroid taxonomy and demarcation to meet the requirements of classification of the increasing new viroids.Our main purpose is to clearly show the latest viroid taxonomy and demarcation.Based on a short introduction to viroids,we comprehensively summarize the principle of viroid taxonomy and offer the explanation for the recent modifications.