Abstract: A free surface tropical Pacific ocean GCM with high resolution developed at the Institute of Atmospheric Physics is used to simulate the La Niña event, one of the important phase in the El Ninño/Southern Oscillation (ENSO) cycle. The model covers the tropical Pacific Ocean between 30°N and 30°S with horizontal grid spacing of 1° in latitude and 2° in longitude. There are 14 vertical layers with eight layers in the top 200 m. The model includes the salinity and adopts the Richardson number dependent vertical mixing parameterization related with currents shear and stratification stability. Observed atmospheric forcing fields, sea surface wind stress, heat flux and water flux (evaporation minus precipitation),force the model over the periods of 1984-1989. Numerical simulation of the 1988 La Niña event is presented in the paper with emphasis on describing the time and space evolution of sea level, currents and temperature, and on contrasting the differences between the La Niña event and the El Ninño episodes. Also. some comparisons between the model results and corresponding observations are given.