The mbedOS is a real-time operating system launched by ARM in 2014 for intelligent terminals and IoT nodes. It is mainly used in embedded systems with the high real-time response time. The study analyzes the common problems of transplantation and gives specific migration steps based on the in-depth analysis of the basic functions of mbedOS, scheduling mechanism, delay function mechanism, and communication mechanism between tasks. This work is based on the portable mbedOS engineering framework. On the basis, the mbedOS is implemented in different cores of ARM Cortex-M series and different MCU transplantation. The analysis of the common problems of transplantation between different development environments are given and the basis for the application research of mbedOS are provided. It effectively reduces the difficulty of mbedOS transplantation and can also provide reference for other RTOS transplantation.