The invention discloses preparation of a ruthenium-modified Ir/C catalyst and application of the ruthenium-modified Ir/C catalyst to citral hydrogenization. The catalyst comprises an active carbon carrier, and an active component comprises Ir nano particles and Ru nano particles, wherein the carrying capacity of the Ir nano particles is 1.0 to 5.0 percent, and the carrying capacity of the Ru nano particles is 0 to 4.0 percent. The invention further discloses a preparation method of the ruthenium-modified Ir/C catalyst. The preparation method comprises the following steps: firstly, treating active carbon through nitric acid, then carrying the active component including iridium and auxiliary ruthenium to obtain a catalyst precursor, and carrying out drying and reducing. As Ru replaces part of Ir, the catalyst disclosed by the invention is lower in cost, and also has higher catalysis activity and selectivity; furthermore, the catalyst can be used indiscriminately for multiple times, so that the production cost is reduced. When the catalyst is applied to citral hydrogenization to synthesize nerol, the raw material conversion rate is 100 percent, and the nerol/geraniol selectivity is up to 98.0 percent; the reaction process is mild in condition, and can completely meet the industrial production requirement.