Abstarct: Technology progress in the field of wireless communications technology, electronics and energy-saving design, and also tend to use low-priced products with high performance, leading to the creation od one of the most widely used network as the wireless sensor network. According to one of the main objectives of these network to collect and send information to the main node about the environment, the most important issue here is the quick and accurate delivery of data packets with the lowest energy consumption and as well as an increase in applications of this network in human life, the quality of service that these networks offer are very important. In this study, after the introduction of wireless sensor networks and their applications, the definition of quality of service in these networks will be illustrated. Then by discussing the future restrictions, we express the most important routing algorithms in wireless sensor networks due to the provision of service quality standards. After that, we introduce a routing algorithm baxsed on genetic algorithm, and the results of the proposed algorithm with the comparison to one of the new existing algorithms further verify improvement in the quality of service. It's necessary to consider all laxyers of the network to improve the quality of service in wireless sensor networks.But in this thesis, we concentrate on network laxyer, and we have tried to select the appropriate routing algorithms to provide and increase the necessary requirements of the quality of the services such as packet delay and power consumption nodes, according to the inherent limitations of wireless sensor networks.