A　novel　and　facile　microfluidic　approach　for　single-step　fabrication　of　W/O　Janus　droplets　and　W/O/W　double　Janus　emulsions　droplets　is　developed.　The　influence　of　flow　rate　on　the　component　proportion,　size　and　frequency　of　the　emulsion　droplets　is　experimentally　investigated.　The　proportion　of　the　two　components　in　the　droplet　is　positively　correlated　with　the　flow　rate　ratio　of　two　dispersed　phases,　Q(W1)/Q(W2).　In　the　process　of　W/O/W　double　emulsion　formation　containing　two　different　reagent　cores,　the　droplet　diameter　changes　abruptly　because　of　the　translation　of　droplet　generation　mode.　In　the　dripping　regime,　the　inner　and　outer　diameters　of　the　double　emulsion　decrease　linearly　with　the　increase　of　the　outer　phase　flow,　and　the　components　of　the　core　droplets　remain　constant.　With　the　uniform　number　of　cores,　the　frequency　of　inner　droplet　generation　is　positively　correlated　with　the　discrete　flow　rate,　but　negatively　with　the　increase　of　the　number　of　cores.　(C)　2019　Elsevier　Ltd.　All　rights　reserved.