This paper describes a novel free-flow electrophoresis (FFE), which is joined with gratis gravity, gas cushion injector (GCI) and self-balance collector instead of multiple channel pump, for the purpose of preparative purification. The FFE was evaluated by systemic experiments. The results manifest that (i) even though one-channel peristaltic pump is used for the driving of background buffer, there is still stable flow in the FFE chamber; (ii) the stable flow is induced by the gravity-induced pressure due to the difference of buffer surfaces in the GCI and self-balance collector; (iii) the pulse flow of background buffer induced by the peristaltic pump is greatly reduced by the GCI with good compressibility of included air; (iv) the FFE can be well used for zone electrophoretic separation of amino acids; (v) up to 20 inlets simultaneous sample injection and up to five to tenfold condensation of amino acid can be achieved by combining the FFE device with the method of moving reaction boundary. To the best of authors' knowledge, FFE has not been used for such separation and condensation of amino acids. The relevant results achieved in the paper have evident significance for the development of preparative FFE.