The significance of the software quality assurance for high operational risk systems is concerned with the increasing complexity and functionality of the software of the software systems important for nuclear power plants safety. In the paper, there are considered possible consequences concerned with violations of the technological process of the software development; ways of achieving the required software quality on the basis of software verification and validation at all stages of the life-cycle; approaches to defining the quality, procedures of software quality justification, models of analysis requirements to systems in the part of the software.