Abstract: Restrictions in intersections after left-turning traffic control often lead to ring roads in urban traffic networks.Classic iterative algorithm can not be used to point out the optimal path containing circle, and the cumbersome network topology conversion or data structure should be firstly processed.This study shows that P and U-shaped circle roads in the optimal path can be solved by Floyd algorithm.And the judging rules for prohibited routes constructed by forward and reverse path indicators can be implemented simultaneously with Floyd iterative algorithm.In terms of those mends, the algorithm can automatically give out accurate results for both the paths with loop and paths in general network.Due to the original network topology unchanged, this method will be particularly easy to use, and has high efficiency.