Mobile applications (APPs) are adopted and downloaded widely around the world. Those APPs are those for examples linking to enterprise applications, management information systems, education systems, and healthcare systems. Thus, the importance of potential development APPs is hung. The objective of this study is to elicit design principles for ensuring the interactivity of smart parking APPs to be used especially in the city. This study conducted a systematic review on the past literature of interface design and case studies on seven smart parking APPs on the market in order to develop a design framework for smart parking APPs, which include a list of design principles. Then, four experts of APP design were involved in a series of interviews to improve the readability and usability of the framework. Finally, this study identified 11 principles for improving the interactivity of smart parking APPs, which are useful to the situation when users need to interact with a smart phone urgently in a small-touch-screen environment