After analyzing the effect of light path's,path's congestion and idle wavelengths in the network,one novel dynamic optical routing algorithm is proposed.According to amount of available free wavelengths in the network,services will be distributed in the shortest paths,the least congestion paths or the paths with the maximum ratio of free wavelengths in paths to hops.If idle resources reduce,probality of shorter paths' selection will increases.Otherwise,probability of less congestion paths will increase.The results of NSF network simulation show that the blocking probability of proposed algorithm decrease 19.1% and 12.7%,respectively compard with traditional algorithms-FAR and FPLC.