The　rapid　development　of　high　technology-such　as　space　exploration　and　electric　vehicles-urgently　requires　ultra-wide　temperature　multilayer　ceramic　capacitors　(UWT　MLCCs)　to　achieve　reliable　operation　of　electronic　circuits　in　harsh　environments.　However,　simultaneously　achieving　high　dielectric　permittivity,　low　dielectric　loss,　and　ultrahigh　thermal　stability　has　been　a　major　challenge　for　practical　dielectric　ceramics.　The　co-firing　matching　of　the　internal　electrode　and　the　dielectric　ceramic　is　also　an　important　factor　that　affects　the　reliability　of　UWT　MLCCs.　Herein,　through　multifaceted　modification-i.e.,　composition　design　related　to　the　modulation　of　the　local　polar　nanoregions　(PNRs)　and　optimizing　device　sintering　in　the　context　of　the　compatibility　of　the　heterogeneous　interface-these　concerns　have　been　well-addressed.　A　new　lead-free　dielectric　system　(1-x)　(0.56Na(0.　5)Bi(0.5)TiO(3)-0.14K(0.5)Bi(0.5)TiO(3)-0.3NaNbO(3))-xCaZrO(3)　(NKBTNN-xCZ)　dominated　by　P4bm　PNRs　was　designed　and　corresponding　UWT　MLCCs　with　reliable　Pt　internal　electrode　interface　bonding　were　fabricated　by　optimizing　the　sintering　temperature.　A　record-high　dielectric　permittivity　(epsilon(r)　=　839　+/-　15　%)　and　low　dielectric　loss　(tan　delta　＜=　0.02)　was　achieved　over　an　ultra-wide　temperature　range　from　-70　degrees　C　to　337　degrees　C　for　NKBTNN-0.063CZ　UWT　MLCCs.　This　work　suggests　that　multifaceted　modification　should　be　generalized　for　construction　of　high-performance　UWT　MLCCs.