An I2C multi-slot circuit system includes a plurality of I2C slots for receiving a plurality of slave processors, a CPU, a logic control unit, and a I2C switch unit. The CPU determines an address of one of the I2C slots which to-be-transmitted data will be transmitted to, and generates a first logic control signal according to the determined address. The logic control unit enables the one of the I2C slots which the to-be-transmitted data will be transmitted to according to the first logic control signal. The I2C switch unit receives and transmits I2C signal converted from the to-be-transmitted data by the CPU to the I2C slot. A related method is also provided.