Ocean salinity variation provides a new insight into related ENSO expressed by climate variability. In this study, the comparisons of salinity variability and its related dynamical processes responsible for SSTA have been extensively described and analyzed among two strong ENSO, 1997/1998, 2015/2016 and one special ENSO, 2014/2015. The study shows that the development of ENSO is significantly associated with the occurrence and eastward diffusion of large-scale surface salinity anomaly (SSSA) in the western-tropical Pacific. In April of 1997 and 2015 corresponding to two strong ENSO events, there was a significant negative SSSA in the western-central Pacific, and then it moved eastward to the west of the dateline which induced the mixing layer depth (MLD) shallow, and the barrier layer thickness (BLT) thickened, which enhanced the surface warming in the tropical central Pacific and the early warming in the equatorial eastern-central Pacific. Although negative SSSA occurred in April of 2014/2015 weak event in the equatorial western-central Pacific, it did not develop eastward, resulting in weakened thickening process of BLT and weak modulation effect on surface temperature. For salinity change process corresponding to three ENSO events, surface advection and surface forcing caused by fresh water flux (FWF) were the major contributors to salinity budget. Surface advection influenced the former variability of salinity tendency, inducing the occurrence of ENSO signal. The precipitation in the tropical western Pacific played the most significant negative influence on FWF, which made a decisive role in the occurrence of SSSA and in the development of ENSO. Compared with the two strong ENSO events, the early FWF negative anomaly in 2014/2015 did not develop and moved eastward and weakened rapidly, resulting in a slowing of the negative salinity tendency in the western-central Pacific, deepening of MLD, thinning of BLT, and rapid cooling of the surface layer, which inhibited the early warming in the equatorial-eastern Pacific. The results of study demonstrate that the salinity change is closely related to ENSO, and early SSS in the tropical western-central Pacific could be used as the index of SSTA. In particular, SSSA not only affects the strength of ocean SSTA, but also could be used as a precursor to judge the development and strength of ENSO.