A compact and highly b-oriented MFI monolayer was fabricated with a novel phase-segregation-induced self-assembly method. When MFI microcrystals were dispersed uniformly in an appropriate dispersant (sec-butanol) containing a trace amount of binding agent (linoleic acid), these microbuilding blocks were spontaneously self-assembled into a compact monolayer at an air liquid interface. In particular, it was observed that the binding agent took effect only after being phase-segregated from the aqueous solution. The influence of the kind of dispersants and binding agents on the final morphology of the as prepared MFI monolayers was discussed. On the basis of these results, a mechanism was proposed to elucidate the driving force for the compact and oriented assembly of these MFI building blocks at the air water interface.