Powder molded compacts, characterized by low powder filling rates such as Metal Injection Molding (MIM), often exhibit problems with deformation during sintering due to their large shrinkage and low strength. In this study, the Digital Image Correlation method (DIC) was used for in-situ observation of sintering in Ni powder compacts fabricated by MIM to investigate their large-deflection deformation behavior. As a result, it was revealed that there is a time point when the deviatoric vertical strain in the longitudinal direction becomes tensile across the entire base of the molded compacts. This strain distribution was not symmetrical distribution of tensile and compressive strains, as is typically observed in the small deflection deformation of an elastic body. Additionally, a finite element analysis was performed using a plastic deformation model for porous materials, and it was confirmed that similar results were obtained.