Requirement engineering is one of the critical phases in the software systems development process. Functional Requirements (FR) and Non- Functional Requirements(NFR) are two of the fundamental requirements in software systems that are observed in the classifications of most of the researchers in this field. Conflicting and overlapping among the requirements in both intra and extra communications levels are some of the problems and challenges in the elicitation and prioritization phases. This paper defines and presents a decision strategy called requirements conflicts management strategy (RCMS). This strategy is defined to manage conflict and overlap of NFRs in the prioritization of the constraints satisfaction model for requirements prioritization, known as "CSOP + RP" model, in which the necessary constraints are also applied. RCMS is applied as a pre-processing phase by the requirement analyser and the results are delivered to the system manager in the "CSOP+RP" model. The composition of multiple components, such as conflict catalogue of NFRs and the relation table, the mapping model of NFRs to the domain systems, and precedence of weighted decision units in this strategy, leads to proper management of implicit and explicit knowledge conflicts and applying to overlap. The results show that using the proposed strategy leads to make a better decision, conflict management and overlapping control optimization. Therefore, ambiguities and influencing of NFRs and between NFRs and FRs reduces requirement ranking in the search-based prioritization approach. Furthermore, the system manager facilitated the final list of requirements prioritization. Manuscript profile