A GPIO port for multi-mode application is designed and implemented.On the basis of the traditional GPIO structure,the GPIO adds bidirectional SCR,GGNMOS,GDPMOS and other special structures,while improving the input and output driver structure,so that the port can achieve normal data transmission,but also have a certain ESD protection ability.The 180nm high voltage process makes the GPIO circuit have certain voltage resistance character-istics.The simulation results show that the GPIO can realize the data transmission function of three working modes stably.