With the development of modern science and technology, the Internet of Things has been widely used in many fields, and it involves a wide range of technologies, among which the most important technology is the sensor, the most basic technology. The sensor network node working environment has been very complex and demanding; if slightly relaxed, it will lead to the sensor facing many security risks. Therefore, strengthening the security of wireless sensor networks has become an essential part of the Internet of Things project. This paper mainly starts with an overview of the Internet of Things and wireless sensor networks, analyzes the security challenges and impacts of wireless sensor networks, and discusses the main security threats and countermeasures. The purpose is to implement wireless sensor network security strategies for Internet of Things applications and build a comprehensive and multi-level security protection system through various means. To ensure that the sensor network can operate stably and safely in a complex environment, Internet of Things technology‘s healthy and sustainable development can be promoted.