The　work　aims　to　study　the　effects　of　different　impact　velocity　and　wettability　gradient　on　droplet　movement　during　the　process　of　droplet　impacting　on　solid　surface.　The　specific　data　for　spreading　and　bouncing　droplets　were　obtained　by　molecular　dynamics　(MD)　simulation,　which　was　difficult　to　be　measured　quantitatively　in　the　experiment　and　had　reference　value　for　guiding　engineering　practice.　The　MD　method　was　used　to　simulate　the　nanodroplet　impacting　on　solid　surface　with　wettability　gradient　at　different　initial　velocities　v0.　The　behavior　of　droplet　impacting　on　solid　surface　was　affected　by　droplet　impact　velocity,　presence　of　impurities　in　the　droplet　and　solid　surface　characteristics.　The　solid　surface　characteristics　mainly　included　wettability,　surface　roughness　and　temperature.　The　wettability　of　solid　surface　could　be　reflected　by　the　contact　angle　of　droplet　surface.　The　wettability　gradient　was　constructed　by　changing　the　gap　of　nano　square　columns　on　solid　surface.　The　smaller　the　square　column　gap,　the　smaller　the　contact　angle,　and　the　better　the　wettability.　When　v0=0.3-1.1　nm/ps,　the　droplet　after　hitting　the　surface　moved　along　the　direction　of　good　wettability　on　the　solid　surface.　When　v0=0.3-0.5　nm/ps,　the　droplet　was　hindered　by　the　pinning　effect　and　hardly　spread.　When　v0=0.7-1.1　nm/ps,　the　droplet　underwent　secondary　spreading.　Owing　to　the　effect　of　initial　kinetic　energy　and　pinning　effect　of　the　droplet,　two　inflection　points　were　observed　in　the　curve　of　moving　velocity　vt　when　the　droplet　centroid　left　the　gradient　surface.　The　x-direction　velocity　vt　of　the　droplet　leaving　the　gradient　surface　was　mainly　related　to　the　initial　velocity　v0　and　the　total　spreading　time　T　of　the　droplet.　The　x-direction　velocity　vt　increased　with　the　increase　of　the　initial　kinetic　energy　of　the　droplet.　vt　decreased　with　the　increase　of　T,　because　the　kinetic　energy　of　droplets　was　consumed　more　in　the　spreading　process.　When　v0=1.2-1.5　nm/ps,　the　droplet　bounced　after　hitting　solid　surface.　At　this　time,　the　velocity　component　of　the　droplet　in　the　vertical　direction　of　v0　increased　with　the　increase　of　v0,　and　the　relationship　between　them　was　linear,　while　the　velocity　component　in　the　horizontal　direction　of　v0　remained　unchanged,　which　corresponded　to　the　fixed　value　of　0.017　nm/ps.　The　bouncing　velocity　v　and　angle　α　of　droplet　increased　with　the　increase　of　v0.　In　the　process　when　a　droplet　impacts　on　a　solid　surface　with　wettability　gradient,　the　relationship　between　maximum　spreading　factor　βmax　and　v0　is　proposed　to　be　approximately　linear.　After　the　impact,　the　low-velocity　droplets　are　captured,　which　then　move　along　the　direction　of　good　wettability.　The　relationship　between　vt　and　v0　in　different　impact　velocity　ranges　is　proposed　herein.　The　high-velocity　droplets　bounce　along　the　side　with　good　wettability.　Furthermore,　the　relationship　among　droplet　bounce　velocity,　angle,　and　v0　is　proposed,　respectively.　©　2022,　Chongqing　Wujiu　Periodicals　Press.　All　rights　reserved.