The theoretical arithmetic for planning of radio relay links has been prescribed in ITU-R and our country criterion. This paper improved the arithmetic of EMI and outage probability in order that computers can deal with it effectually. A schema employing Object-Oriented Software Engineering Method to develop a toolbox software is put forward to automate the course of planning of radio relay links. Applications of Object-Oriented Analysis (OOA), Object-Oriented Design (OOD) and Object-Oriented Programming (OOP) in the software development were discussed. The function of the toolbox software proved to be highly effective.