Within the framework of R&D project “Information support of research by scientists and specialists on the basis of RNPLST Open Archive as the system of scientific knowledge aggregation”, the RNPLS&T carries on the analysis of general characteristics and features of and defining standard requirements for the LIS search interfaces. The author attempts to develop the array of the requirements for modern web-based interfaces of e-catalogs, to classify and formulate them more specifically, and to substantiate these requirements. She proposes the following classification of the requirements: general requirements, requirements for search functionality structure, requirement for content enrichment, requirement for the system of search user support, requirements for applying recommendation system and existence of auxiliary user support. The author also suggests the ways to improve search interfaces of e-catalogs, in particular, to unify and differentiate search instruments, to obtain additional search options, to implement different types of user support more intensively, and to create effective multifunctional recommender systems. The proposed recommendations may be used for search interfaces of library information systems.