Open ocean deep convection is consisted with small scale processes such as downward plumes and baroclinic eddies, and non-hydrostatic models are usually used. In this study, we have investigated the structures of deep convection using a plume resolving hydrostaticgeneral ocean circulation model, GFDL-MOM3, by performing preconditioning experiments, uniform cooling of a cyclonic gyre. The results have compared with those from large eddy simulation. As in large eddy simulation, when the strength of azimuthal velocity is large enough, a cyclonic gyre brakes into baroclinic eddies causing large lateral transfer of heat. The vertical stratification decrease over time due to the cooling at the surface, but water columns remain well stratified. From temperature or velocity sections, one can identify individual plumes. As in LES when cooling is strong or the azimuthal velocity is weak enough, convectively mixed layer deepens locally without significantradial exchange, and water columns become homogeneous rapidly in the vertical. Unlike LES, one cannot identify individual convective plumes partly because a convective adjustment schemethat does not allow static instability is used. By comparing results with different convection schemes and LES while focusing on horizontal mixing and restratification, the effect of hydrostatic assumption and convection schemes on deep convection is also studied.