Efficient fabrication of metal organic framework (MOF) membranes is important for their broad applications in molecular separations. However, current approaches for MOF membrane fabrication are usually time-consuming due to the slow, random nucleation and crystal growth, particularly the lack of in-situ defect healing ability. Here, we report an additive-accelerated electrodeposition method, which allows ultrafast fabrication of MOF membranes through the synergy of electric field and catecholamine additives. The strong electric field facilitates the directed nucleation of MOF on the substrates while the multifunctional additives accelerate the MOF crystallization, growth and grain-boundary defect healing. Consequently, we fabricate well-intergrown, uniform MOF (ZIF-8) membranes with an ultrathin thickness of ~180 nm in 30 seconds, which is the most rapid fabrication of MOF membranes till now. The membranes exhibit superior C3H6/C3H8 separation performance with a C3H6 permeance of 145 GPU and a C3H6/C3H8 separation factor of 151 as well as good stability at high pressure of 7 bar, and the ultrafast membrane fabrication can be achieved on commercial ceramic substrates, exhibiting the potential for practical applications. This work may establish a platform for fast and controllable fabrication of MOF membranes as well as many other membranes based on metal-coordination chemistry.