In　this　paper,　the　IC10　alloy　joints　are　prepared　by　laser　welding.　The　effect　of　process　parameters　on　thermal　crack　is　discussed,　and　the　formation　mechanism　of　welding　thermal　crack　in　different　types　during　laser　welding　of　IC10　alloy　are　analyzed　by　micro　means.　The　microstructure,　element　distribution　and　phase　composition　of　the　thermal　cracks　are　studied.　When　the　laser　scanning　direction　is　perpendicular　to　the　grain　growth　direction　of　the　substrate,　the　crack　sensitivity　is　greater.　With　the　increase　of　laser　power　and　the　decrease　of　shielding　gas　flowing,　the　crack　sensitivity　is　also　greater.　A　faster　welding　speed　could　cause　thermal　stress　and　increase　crack　sensitivity.　The　choice　in　an　appropriate　laser　scanning　speed　range　could　effectively　control　the　tendency　of　crack　formation.　According　to　the　analysis　of　the　formation　mechanism　of　different　cracks,　the　results　of　SEM　and　EDS　showed　that　IC10　alloy　was　susceptible　to　crystallization　cracking　due　to　the　high　content　of　low　melting　point　eutectic　between　grains　and　grain　boundaries,　and　the　tendency　to　produce　liquefaction　crack　becomes　greater　when　coarse　carbides　precipitate,　both　types　of　cracks　belong　to　the　thermal　cracks　caused　by　liquid　films.　In　IC10　alloy,　ductility　dip　cracking　(DDC)　is　thermal　crack　caused　by　the　sharp　drop　of　intergranular　plasticity,　which　is　closely　related　to　the　state　of　grain　boundaries　and　interstitial　phase　precipitated　from　grain　boundary.　The　crack　susceptibility　of　DDC　cracks　is　easier　to　control　than　the　above　mentioned　two　type　thermal　cracks.