Abstract: An improved method to research simulation graph of the bidirectional double-loop networks G（N；±1，±s） is presented based on Cartesian coordinates which has been creatively used.Based on these researches，the definition of the best bidirectional double-loop networks G（N；±1，±s） is given whose diameter and average diameter are both optimal and the relationship is also studied between diameter and step s.At last，the simulation of the graph of the best bidirectional double-loop networks G（N；±1，±s） is given for any given diameter.Compared with L-shaped tile simulation which can not be used in the bidirectional double-loop networks directly，this method improves the research level of the bidirectional double-loop networks greatly，and has not been reported in existing documents.