The relative arrival delay estimation of the eigenrays is the key part of the matchedfield processing based on acoustic ray modeling (MFPARM). In this paper, the influence of the source position changing and SSP perturbation on the relative arrival time delay of eigenrays is studied. Based on the Shallow Water’06 experimental environment model (the literature retrieval results) and SSP data measured during experiment, it is found that the influences of both the source position change and SSP perturbation on the relative arrival time delay of eigenrays are similar. The similarity can provide some reference value for robust MFPRAM.