The patients benefit from the ubiquitous healthcare system by accessing healthcare services ubiquitously in unfamiliar environments. However, the patients confront the problem that they usually do not have enough knowledge about the healthcare providers in these unfamiliar environments. By collecting, distributing and aggregating feedbacks of the healthcare providers' past behaviors, reputation system is therefore a method to help the patients choose reliable healthcare providers as well as help the healthcare providers build up the trustworthiness and attract more patients in unfamiliar environments. This paper contributes to analyze the importance of using reputation system in ubiquitous healthcare. We analyze the relationship of security, trust and reputation in ubiquitous healthcare in details. We also illustrate how to use reputation system on decision making by analyzing a scenario. The requirements and challenges of reputation system in ubiquitous healthcare are addressed in details based on the analysis of the scenario.