A new method to research the diameter of the bidirectional double-loop networks G（N;±1

±s） was presented based on cartesian coordinates.Using this method

the limited bound of diameter of the bidirectional double-loop net-works G（N;±1

±s） presented by Boesch and Wang was certified and the limited bound of average diameter was given.At last

the simulation of the graph of bidirectional double-loop networks G（N;±1

±s） for any given N

s was given.Com-pared whith L-shaped tile simulation which can not be used in the bidirectional double-loop networks directly

this method improved the research level of the bidirectional double-loop networks greatly.