This study is to present two Chinese siblings who were diagnosed with congenital disorders of glycosylation (CDG) IIb because of mannosyl-oligosaccharide glucosidase (MOGS) deficiency. The siblings visited our hospital due to "pulmonary infection". Facial dysmorphism including long eyelashes, blepharophimosis, depressed nasal bridge, and high palate was noted. Head MRI of the elder sister showed increased signals on T1W1, bilateral frontal gyrus stenosis, and thin corpus callosum. Both cases presented progressive hepatomegaly and elevated hepatic enzymes. Low immunoglobulin was discovered in the siblings. Compound heterozygous variants of NM_006302:c.1239_1267dup,p.Asp414Leufs*17, c.544 G > A,p.Gly182Arg, and c.1698C > A,p.Asp566Glu in MOGS were identified. Structural modeling demonstrated that the mutations were pathogenic to MOGS. Our study enriched the genetic and phenotypic spectrum of MOGS-CDG, and for children with facial dysmorphism, postnatal dyspnea, seizures, motor developmental delay, hypotonia, and immunological or gastrointestinal dysfunction, this disease should be highly suspected.