Abstract-In this paper a CommShell for Arduino has been proposed and designed. CommShell is a shell program running on the Arduino platform, accepting interactive commands from its simulated serial communication port. With the help of Arduino CommShell, users can communicate with Arduino using pre-defined commands and implement mechatronic instrumentation and control tasks without writing and compiling codes. Arduino CommShell is initiated with the idea of easier in-class demonstration on mechatronic system control. However it is also very useful for beginning engineering students to learn the concepts of Mechatronic system or Arduino beginners to get familiar with Arduino. Arduino CommShell is designed as an open architecture which is composed by a command interpreter, a function library and a base set of Arduino API. The function library can be extended to make the shell accept more commands, or be customized to do jobs on designated areas. Experiments and examples have been conducted to verify its usefulness, easiness and extendibility.