Digital Library (DL) development is faced with many challenges which cannot be overcome all at once. In such cases which are so complex, maturity models are utilized. In a maturity model, features of a phenomenon are classified into few levels so that improving or realizing the features of each level is the prerequisite of going to the next level. DL can also be approached by maturity model more efficiently and effectively. Since the maturity model for DL has not been designed yet, first, a literature review of the DL and maturity models using a qualitative approach and meta-synthesis method was done. According to the findings of the literature review, the maturity characteristics of DL are proposed to be a basis for designing DL maturity model. Since the concept of maturity and DL is extensive and has several dimensions, meta-synthesis has been found as a suitable method for comprehensive integration of the models offered in other areas with the existing literature in the field of DL based on their interpretation. To do so, 68 papers (38 in the field of DL and 30 in the field of maturity models in various fields) were selected from the available resources. By analyzing these papers, three categories, seven concepts, and 35 codes obtained as DL maturity features. Among these findings, the focuses of previous studies have been on the use of software/ hardware systems as supporter and enabler of DL and the DL content. The found features, in addition to be a basis for designing of digital library model, can be a tool in the hands of project managers of DL for assessing the status of their projects and planning to achieve higher levels of maturity.