Abstract: In order to improve the reliability of wavelength division multiplexing(WDM),the segmented shared path protection(SSPP) algorithm is usually adopted.It requires equal length segmentation in WDM optical networks and it must obey the shared risk link group(SRLG) constraint.When searching protection path,the SRLG constraint will lead the call blocking probability of the networks to rise.In order to reduce the call blocking probability,a new path protection algorithm,so-called preferential shared path protection(PSPP) was proposed.The simulation of SSPP and PSPP algorithms was done in the discrete event emulation system.The result shows the call blocking probability of the PSPP algorithm is better than that of the SSPP algorithm,and the resource reservation ratio of PSPP is also relatively better.