In recent years, the issue of structural safety has arisen due to the increasing ship repairing and refitting, particularly with regards to large-scale temporary hatch openings applied on deck or bulkhead. These openings lead to a loss of structural continuity, resulting in significant local deformations under higher loads. Therefore, it becomes necessary to implement real-time monitoring of opening deformations during repairs. This study focuses on investigating deformation control for two typical hatch openings on deck by analyzing their behavior under wave bending and torsional moments using finite element analysis. Based on the observed deformation behaviors, indexes such as hatch flatness and variation in diagonal length are proposed for evaluating deformation control. Furthermore, the effects of different hatch sizes on these indexes are examined, leading to an optimization design for opening sizes and locations aimed at achieving effective deformation control.