Nanoparticle-based　materials　(NBMs),　whose　thermal　insulating　performance　is　dominated　by　the　heat　transfer　between　two　neighboring　nanoparticles,　have　attracted　tremendous　attention　in　recent　decades　due　to　their　potential　applications　in　thermal　insulation.　This　work　provides　an　insight　into　the　conductive　heat　transfer　between　two　touching　solid　or　hollow　nanospheres　by　solving　the　gray　phonon　Boltzmann　transport　equation　(BTE).　The　influence　of　some　factors,　including　particle　size,　contact　ratio,　and　shell　thickness　on　the　temperature　distribution　and　effective　thermal　conductivity　of　two　touching　particles,　is　examined.　Based　on　the　thermal　constriction　resistance　theory　and　numerical　results,　a　prediction　model　for　the　effective　thermal　conductivity　of　two　touching　solid　nanospheres　is　then　proposed　and　proved　to　have　high　accuracy　with　a　relative　error　less　than　3.0%.　Finally,　a　brand　new　effective　thermal　conductivity　model　for　two　touching　hollow　nanospheres　with　the　same　form　as　that　of　two　touching　solid　spheres　and　an　acceptable　prediction　error　of　6.5%　is　also　proposed.　©　2020