Grading　the　porous　anode　microstructure,　i.e.,　gradient　anode　is　an　effective　way　to　enhance　the　electrical　performance　of　anode-supported　solid　oxide　fuel　cells　(SOFCs).　This　article　is　the　first　part　of　a　two-part　article　which　presents　a　3D　numerical　model　of　a　gradient　anode　SOFC　and　conducts　a　model　validation　in　comparison　with　the　experiments　for　the　gradient　anode　SOFC　modeling　and　optimizing.　An　experimental　test　setup　was　constructed　first　to　evaluate　the　electrical　performance　of　a　SOFC　button　cell　with　a　gradient　anode.　Then　the　microstructure　characterization　of　each　cell　component　was　obtained　by　combining　the　mercury　porosimetry　with　image　analysis.　Parameters　relating　to　the　microstructure　mainly　included　the　layer　thickness,　porosity,　pore　size,　and　particle　size.　Based　on　the　microstructure　parameters　and　measured　electrical　performances,　the　numerical　model　of　the　gradient　anode　SOFC　button　cell　was　established,　which　related　the　cell　microstructure　to　the　electrochemical　characteristics.　The　results　show　that　the　microstructure　parameters　of　each　cell　component　can　be　quantificationally　obtained　by　the　backscatter　electron　image　analysis.　The　modeled　i-V　and　i-P　curves　at　three　flow　rates　of　fuel　gas　(75/100/125　mL·min−1)　agree　well　with　the　experimental　data.　This　validation　process　indicates　that　the　numerical　model　is　able　to　accurately　describe　the　electrical　performance　of　the　gradient　anode　SOFC　and　it　can　be　further　extended　to　optimize　the　anode　microstructure　distribution.　©　2019,　©　2019　Taylor　&　Francis　Group,　LLC.