Abstract: In recent years, many biosimilars have been approved marketing authorization in our country. When conducting research and evaluation of biosimilar, the quality similarity between the candidate drugs and the original drugs is the key point of "biosimilar", meanwhile it is the basis for clinical and marketing authorization of biosimilar. However, the industry and regulatory agencies are facing many challenges in establishing quality "similarity assessment criteria", such as: limited batches of original drugs; quality drift caused by manufacture process changes in the life cycle; analytical method of critical quality attributes is different from different manfactures; statistical methods used for establishing assessment criteria are difficult to unify. In the article, the data obtained from 69 lots of chemistry, manufacturing and control (CMC) dossier of trastuzumab originator company and dossiers of 9 biosimilar companies were analyzed. Furthermore, combined with the risk identification of the critical quality attributes of the product, quality "similarity assessment criteria" have been proposed. This standard has been verified by the disclosure of biosimilar quality data, aim to promote the development and evaluation of trastuzumab biosimilar.