Droplet　merging　and　splitting　are　important　droplet　manipulations　in　droplet-based　microfluidics.　However,　the　fundamental　flow　behaviors　of　droplets　were　not　systematically　studied.　Hence,　we　designed　two　different　microstructures　to　achieve　droplet　merging　and　splitting　respectively,　and　quantitatively　compared　different　flow　dynamics　in　different　microstructures　for　droplet　merging　and　splitting　via　micro-particle　image　velocimetry　(micro-PIV)　experiments.　Some　flow　phenomena　of　droplets　different　from　previous　studies　were　observed　during　merging　and　splitting　using　a　high-speed　microscope.　It　was　also　found　the　obtained　instantaneous　velocity　vector　fields　of　droplets　have　significant　influence　on　the　droplets　merging　and　splitting.　For　droplet　merging,　the　probability　of　droplets　coalescence　(eta)　in　a　microgroove　is　higher　(50%　＜　eta　＜　92%)　than　that　in　a　T-junction　microchannel　(15%　＜　eta　＜　50%),　and　the　highest　coalescence　efficiency　(eta　=　92%)　comes　at　the　two-phase　flow　ratio　e　of　0.42　in　the　microgroove.　Moreover,　compared　with　a　cylinder　obstacle,　Y-junction　bifurcation　can　split　droplets　more　effectively　and　the　droplet　flow　during　splitting　is　steadier.　The　results　can　provide　better　understanding　of　droplet　behaviors　and　are　useful　for　the　design　and　applications　of　droplet-based　microfluidics.