Abstract: In this work, a self-suction phase-dispersing reactor was devised as a substitute for sample cell of laser particle instrument. The new self-suction phase-dispersing reactor can produce good dispersing effect at low shear force. It is in favor of keep some biological substances bioactivity such as proteins. It can exclude denature of strong agitation basically and reflect systems inherent emulsification property. Inseting sample cell at deferent height, we can get particle-size distribution in situ. Moreover after add some surfactants, we can investigate particle-size distribution of emulsions instantaneously during emulsification, demulsification, flocculation process.