The extraction of penicillin G from an aqueous solution with butyl acetate (BA) and tributyl phosphate (TBP) as extractants was carried out at pH 4 with spontaneous suction phase-dispersing (SSPD) extractors under various operating conditions. Four kinds of SSPD extractors were tested with results compared to those obtained by using an extractor with mechanical stirrers. Rotation speed and different extraction systems were found to influence the penicillin recovery and the stability of emulsion formed during extraction. The percentage of extraction under optimum conditions was 91% without formation of emulsion. The laser particle size measurement instrument combined with SSPD can be used to measure the emulsion droplet size in situ.