The invention provides a communication system and a communication method. The communication system comprises a first running gear, a second running gear and a broadcaster, wherein the first running gear is provided with a first golden key; the second running gear is provided with a second golden key; the broadcaster is used for broadcasting transmission data and first validation data to the first running gear and the second running gear, wherein the first running gear carries out first validation program processing on the transmission data through the first golden key so as to obtain a first confirmation code, and the first running gear carries out second validation program processing on the first validation data through the first golden key so as to obtain a second confirmation code. When the first confirmation code is equal to the second confirmation code, the broadcaster is trusty for the first running gear, and when the first confirmation code is unequal to the second confirmation code, the broadcaster is untrusty for the first running gear.