The aim of the study was to evaluate the effect of sucrose, formic acid and lactic acid bacteria (LAB) inoculant on chemical composition and in vitro rumen digestibility of drooping wild ryegrass (Elymus nutans Griseb.) silage. Fresh drooping wild ryegrass was harvested at boot stage and ensiled with: 1. control (untreated), 2. 20 g · kg⁻¹ sucrose (S), 3. 3 g · kg⁻¹ formic acid (FA) and 4. 0.005 g · kg⁻¹ commercial LAB inoculant (LP). The addition of all three additives increased the Flieg point, and decreased pH and butyric acid content (P < 0.05). There was lower ammonia N content in silages treated with S and FA. On the other hand, LP addition elevated lactic acid content with simultaneous increase of the lactic to acetic acid ratio (P < 0.001). The silages were further anaerobically incubated at 39 °C for 48 h with buffered rumen fluid of lactating cows. All three additives increased volatile fatty acid production (P = 0.008). Addition of LP increased average gas production rate and ammonia N content (P < 0.001). In brief, well fermented drooping wild ryegrass silages were obtained by adding LP or S in comparison to FA. LP can be recommended as a silage additive for preparing well fermented silage, and FA could be applied as a regulator additive to control the level of lactic acid produced during drooping wild ryegrass ensiling.