The Zero User Interface (UI)-based automatic speech translation system and method can solve problems such as the procedural inconvenience of inputting speech signals and the malfunction of speech recognition due to crosstalk when users who speak difference languages have a face-to-face conversation. The system includes an automatic speech translation server, speaker terminals and a counterpart terminal. The automatic speech translation server selects a speech signal of a speaker among multiple speech signals received from speaker terminals connected to an automatic speech translation service and transmits a result of translating the speech signal of the speaker into a target language to a counterpart terminal.