The　evolution　of　austenite,　acicular　ferrite,　upper　bainite　and　martensite,　and　the　nucleation　of　inclusions　in　the　microstructure　of　high-strength　steel　deposited　metals,　was　systematically　investigated　using　three　kinds　of　A5.28　E120C-K4　metal-cored　wires　with　various　rare　earth　Pr　contents.　Grain　structure　evolution　in　the　process　of　high　temperature,　dispersoid　characteristics　of　inclusions　and　the　crystallographic　characteristics　of　the　microstructure　were　assessed.　Compared　with　no　addition　of　Pr6O11,　adding　1%Pr6O11　resulted　in　refined,　spheroidized　and　dispersed　inclusions　in　the　deposited　metal,　leading　to　an　increase　in　the　pinning　forces　on　the　grain　boundary　movement,　promoting　the　formation　of　an　ultra-fine　grain　structure　with　an　average　diameter　of　41　mu　m.　The　inclusions　in　the　deposited　metals　were　Mn-Si-Pr-Al-Ti-O　after　Pr　addition;　the　average　size　of　the　inclusions　in　the　Pr-containing　deposited　metals　was　the　smallest,　while　the　number　and　density　of　inclusions　was　the　highest.　The　size　of　effective　inclusions　(nucleus　of　acicular　ferrite　formation)　was　mainly　in　the　range　of　0.6-1.5　mu　m.　In　addition,　the　content　of　upper　bainite　decreased,　while　the　percentage　of　acicular　ferrite　increased　by　24%　due　to　the　increase　in　the　number　of　effective　inclusions　in　the　Pr-containing　deposited　metals　in　this　study.　This　study　shows　that　the　addition　of　1%　Pr6O11　is　efficient　in　achieving　fine　interlaced　multiphase　with　an　ultrafine-grained　structure,　resulting　in　an　enhancement　of　the　impact　toughness　of　the　deposited　metal.