High-temperature　in　situ　fatigue　experiments　were　carried　out　on　the　P/M　superalloy　FGH96　containing　SiO2　inclusions.　The　experimental　results　indicated　that　cracking　occurred　first　on　an　inclusion　itself,　and　then　local　misorientation　and　dislocations　aggregated　at　the　crack　tips　to　prompt　crack　propagation　into　inner　alloy.　The　annealing　twins＇　Schmidt　factor　was　lower　than　its　surrounding　alloys　and　this　structure　hinder　crack　propa-gation　by　changing　the　crack　direction.　Aggregation　of　plastic　strain　and　orientation　variation　were　found　in　the　crack　tip　to　prompt　cracking.　Microtwins　induced　by　single-layer　and　multilayer　atomic　derangement　along　the　＜112＞　twin　direction　on　the　(1　1-1)　plane　were　observed　at　the　crack　tip,　and　an　atomic-scale　microtwins　mechanism　of　inclusion-induced　microcrack　propagation　was　proposed.　In　conclusion,　in　situ　crack　experiments　provided　intrinsic　clues　for　understanding　inclusion-induced　cracking　and　its　propagation.