Activity-Oriented context-aware (AOCA) applications organize environment resources to support the smooth performing of user activities. These applications are developed with a light-weight and incremental method in order to deal with the openness of the environment and requirements related to user activities. In contrast to the methods which attempt to deal with information from an overall level, AOCA applications allow different developers take part in the development in different time. However, this method may lead to more problems such as inconsistency. These problems are difficult to be detected in the development phase. This study focuses on using runtime verification to enhance the reliability of AOCA applications. In this paper, a method is first proposed for specifying AOCA application runtime status and describing system-level and application-level properties. Next, an AOCA application monitor is designed and implemented. Moreover, a case study and a performance evaluation are described to demonstrate the usability of this method.