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We present the results of a systematic search for molecular outflows in 68Very Low Luminosity Objects (VeLLOs) from single-dish observations in COisotopologues which find 16 VeLLOs showing clear outflow signatures in the COmaps. With additional three VeLLOs from the literature, we analyzed the outflowproperties for 19 VeLLOs, identifying 15 VeLLOs as proto-Brown Dwarf (BD)candidates and four VeLLOs as likely faint protostar candidates. The proto-BDcandidates are found to have a mass accretion rate ($\sim 10^{-8} - 10^{-7}$$\rm M_{\odot}$ yr$^{-1}$) lower than that of the protostar candidates($\gtrsim 10^{-6}$ $\rm M_{\odot}$ yr$^{-1}$). Their accretion luminosities aresimilar to or smaller than their internal luminosities, implying that manyproto-BD candidates might have had either small accretion activity in aquiescent manner throughout their lifetime, or be currently exhibiting arelatively higher (or episodic) mass accretion than the past. There are strongtrends that outflows of many proto-BDs are less active if they are fainter orhave less massive envelopes. The outflow forces and internal luminosities formore than half of the proto-BD candidates seem to follow an evolutionary trackof a protostar with its initial envelope mass of $\sim$0.08 $\rm M_{\odot}$,indicating that some BDs may form in less massive dense cores in a way similarto normal stars. But, because there also exists a significant fraction (about40%) of proto-BDs with much weaker outflow force than expected by the relationsfor protostars, we should not rule out the possibility of other formationmechanism for the BDs.

CO Outflow Survey of 68 Very Low Luminosity Objects: a Search for Proto-Brown Dwarf Candidates