Big data in healthcare development and application are more and more important. In this study, firstly, we explained the four V's: volum, variety, velocy, and veracity in big data. Secondly, we used the four V's definition to introduce what kind of healthcare data. Thirdly, we talked about the application of big data in healthcare. Fourly, we explained the application of the National Health Insurance Research Database in Taiwan. Finally, we introduced future developments of big data in healthcare.