The　conversion　of　carbon　dioxide　has　become　a　hot　topic　in　the　world　today.　Here,　we　adopt　the　strategy　of　in-situ　electrochemical　transformation　to　reduce　layered　bismuth　oxide　formate　nanoflowers　(BiOCOOH　NFs)　self-assembled　with　nanosheets　synthesized　by　simple　solvothermal　method　to　porous　bismuth　nanoflowers　(p-Bi　NFs)　with　a　large　number　of　lattice　dislocations.　Specifically,　1.0　g　Bi(NO3)(3).5H(2)O　was　ultrasonically　dissolved　in　10　mL　N,N-dimethylformamide　(DMF),　then　70　mL　deionized　water　was　added　to　the　above　solution,　and　the　resulting　solution　was　ultrasonicated　for　10　min　at　room　temperature　to　ensure　that　all　reagents　were　uniformly　dispersed.　The　resulting　solution　was　then　transferred　to　a　100　mL　Teflon-lined　stainless　steel　autoclave,　kept　at　120　degrees　C　for　20　h,　and　then　naturally　cooled　to　room　temperature.　The　results　show　that　the　minimum　overpotential　of　the　electrochemical　reduction　of　carbon　dioxide　to　formate　is　436　mV.　When　the　catalyst　loading　is　0.5　mg/cm(2),　the　partial　current　density　of　formate　(j(formate))　is　as　high　as　24.4　mA.cm(-2),　which　is　5.5　times　that　of　commercial　bismuth　(Commercial　Bi);　and　the　Faraday　efficiency　(FEformate)　of　formate　is　96.7%　at　-　1.8　V　versus　saturated　calomel　electrode　(vs.　SCE).　The　FEformate　is　over　90%　in　a　wide　potential　window　of　over　500　mV.　Moreover,　the　p-Bi　NFs　electrocatalyst　is　stable　in　formate　production　for　more　than　10　h　in　CO2-saturated　0.5　mol.L-1　KHCO3　electrolyte.　Compared　with　the　normalized　electrochemical　surface　area　(ECSA),　it　was　found　that　the　j(formate)　of　p-Bi　NFs　was　still　about　4.5　times　higher　than　that　of　Commercial　Bi.　The　high　catalytic　performance　of　the　catalyst　can　be　attributed　to　the　unique　micro/nano　hybrid　structure　derived　from　the　lattice　collapse　and　reconstruction　of　precursors,　resulting　in　porous　and　rough　surface　and　containing　high　density　of　active　sites　with　lattice　dislocations　and　defects.　This　study　provides　new　insights　into　designing　and　synthesizing　electrocatalysts　with　high　performance　for　carbon　dioxide　reduction　to　formate.