Seed germination is critical for successful crop production, and the sensitivity to pH and salt stress depends on the plant’s tolerance mechanisms. In view of the characteristics of calcium-rich and acidic soils in the karst areas of Guizhou Province, China, the effects of pH stress and calcium stress on the seed germination characteristics of three herbages were studied with the goal of exploring and revealing the mechanism of adaptation of the three herbages to an acidic soil environment and providing a theoretical basis for the selection and cultivation of acid-tolerant herbages in southwest China. In this study, six concentration gradients of CaCl2, including 0, 25 mmol/L, 50 mmol/L, 100 mmol/L, 150 mmol/L, and 200 mmol/L, and seven pH gradients, including 4.55, 5.35, 6.61, 7.03, 8.0, and 9.18 were established, respectively. The germination rate, germination potential and germination index of the seedlings were measured for each seed germination and seedling growth stage of orchardgrass, perennial ryegrass, and alfalfa, respectively. The results showed that when the concentration of salt stress began to change, the herbage seeds could adapt to salt stress at an appropriate pH condition. When only the pH value or CaCl2 concentration changes, the increase in pH and CaCl2 will inhibit the growth of shoots and roots. Weak acid can promote the growth of shoots and young roots, while alkaline conditions can inhibit their growth. The effect of a low concentration of CaCl2 was not apparent, while a high concentration of CaCl2 clearly inhibited the plants. The optimal pH and CaCl2 of the bud and root lengths changed after the interaction. In conclusion, there is a substantial difference between pH and calcium salt stress, and the interaction between pH and calcium salt concentration has a substantial influence on the salt and alkali tolerance of the three types of seeds.