Salinization of soils or waters is one of the world’s most serious environmental problems in agriculture. Salt stress causes serious damage to many cellular and physiological processes that leads to yield reduction. The study induced salt stress using Hoagland solution added NaCl to evaluate its effects on plant growth and biomass allocation of some forage grass in order to identify salt-tolerant species for growing in salt-affected area in the Mekong Delta (MD) of Vietnam. The study also seeks to evaluate the response of leaf chlorophyll (SPAD unit) and proline content in salt-treated plants to varying application of salinity. Four available forage plants, Panicum maximum, Brachiaria ruziziensis, Hymenachne acutigluma, and Pennisetum purpureum, were chosen to study at five salinity levels of 5, 10, 15, 20 g NaCl/L (and 0 g NaCl/L considered as control treatment). They were arranged in a completely randomized design with three replications. The results showed that NaCl inhibited plant growth and biomass of the four studied plants; however, the dry biomass reduction rate (%) of salt-treated plants compared to control plants (without NaCl adding) was lowest in H. acutigluma < P. purpureum < P. maximum < B. ruziziensis. P. purpureum produced the highest biomass followed by H. acutigluma, P. maximum and B. ruziziensis. However, B. ruziziensis accumulated the highest proline content in leaves tissues, while P. purpureum had the lowest amount. The findings of this study showed that H. acutigluma and P. purpureum were the potential candidates for planting as fodder production in the coastal area or salt-affected soils in the Mekong Delta to adapt with climate change situation.