A new diamond-rhombus shaped honeycomb structure (DRSH) with enhanced in-plane performance is proposed in this study. This proposal is based on the application requirements of negative Poisson"s ratio structures in fields such as shipbuilding and aerospace. The structure is designed by introducing combined diamond-rhombus unit cells into a traditional re-entrant honeycomb. It is then constructed via planar array arrangement. The deformation modes, mechanical properties, and energy absorption characteristics of the DRSH under in-plane loading were systematically investigated. This was done using a combined method of quasi-static compression tests and finite element simulations. The research results indicate that the DRSH exhibits a significant negative Poisson"s ratio effect under various re-entrant angles and wall thicknesses. Its plateau stress and specific energy absorption decrease with an increasing re-entrant angle. Conversely, they improve with an increase in wall thickness. These findings demonstrate that the structural performance can be effectively regulated through geometric parameters. Furthermore, sweep frequency tests were conducted on the DRSH-3D structure. The results show that it possesses stable vibration suppression capability under different excitation amplitudes. Its vibration reduction performance is found to be more significant under conditions of higher excitation amplitudes. This study provides a structural reference for the design and application of negative Poisson"s ratio metamaterials.