Recently,　Jia　et　al.　employed　the　index,　modified　remote　sensing　ecological　index　(MRSEI),　to　evaluate　the　ecological　quality　of　the　Qaidam　Basin,　China.　The　MRSEI　made　a　modification　to　the　previous　remote　sensing-based　ecological　index　(RSEI),　which　is　a　frequently　used　remote　sensing　technique　for　evaluating　regional　ecological　status.　Based　on　the　investigation　of　the　ecological　implications　of　the　three　principal　components　(PCs)　derived　from　the　principal　component　analysis　(PCA)　and　the　case　study　of　the　Qaidam　Basin,　this　comment　analyzed　the　rationality　of　the　modification　made　to　RSEI　by　MRSEI　and　compared　MRSEI　with　RSEI.　The　analysis　of　the　three　PCs　shows　that　the　first　principal　component　(PC1)　has　clear　ecological　implications,　whereas　the　second　principal　component　(PC2)　and　the　third　principal　component　(PC3)　have　not.　Therefore,　RSEI　can　only　be　constructed　with　PC1.　However,　MRSEI　unreasonably　added　PC2　and　PC3　into　PC1　to　construct　the　index.　This　resulted　in　the　interference　of　each　principal　component.　The　addition　also　significantly　reduced　the　weight　of　PC1　in　the　computation　of　MRSEI.　The　comparison　results　show　that　MRSEI　does　not　improve　RSEI,　but　causes　the　overestimation　of　the　ecological　quality　of　the　Qaidam　Basin.　Therefore,　the　modification　made　by　MRSEI　is　questionable　and　MRSEI　is　not　recommended　to　be　used　for　regional　ecological　quality　evaluation.