The invention discloses an efficient silver catalyst for preparing ethylene oxide through ethylene oxidation with amino acid as a guiding agent and a preparing method thereof. When the efficient silver catalyst is prepared, a certain amount of amino acid is added to serve as a loading guiding agent of an active assistant such as a silver active component and caesium and/or rhenium, and a silver component and the like forms a membrane provided with even protrusions on the alpha-Al2O3 surface. The efficient silver catalyst has the advantages of being good in activity, high in selectivity, good in stability and the like. According to the preparing method, an existing preparing technology and mode are not required to be too complexly changed, membranoid distribution of the active component silver and the like in the silver catalyst can be achieved, the preparing method is easy to operate, low in cost, high in controllability and easy to operate, and the requirements for improving the silver catalyst selectivity, stability and the like are met.