Aim To evaluate whether the timing of maternal hypoxia during pregnancy influenced cardiac angiotensin converting enzyme （ACE） - angiotensinⅡ （AngⅡ） - angiotensin type 1 receptor （AT₁） in the adult offspring. Methods Pregnant rats were randomly assigned to maternal hypoxia group starting from early period of pregnancy （G1，day 3 to 21 of pregnancy），group starting from middle period of pregnancy （G2，day 9 to 21 of pregnancy），group starting from late period of pregnancy （G3， day 15 to 21 of pregnancy），or control group. There were 6 rats for each group. Rats of maternal hypoxia groups were subjected to hypoxia for 3 hours in low pressure cabin with an oxygen concentration of 10%±1%. The level of cardiac AngⅡ was detected by Enzyme linked immunosorbent assay （ELISA） in the adult male offspring at the age of 3 months and 5 months. The mRNA expression levels of cardiac AT₁，AT₂，collagenⅠand collagen Ⅲ were measured by reverse transcription PCR. The protein levels of cardiac ACE，AT₁，AT₂ and phosphorylated extracellular signal-regulated kinase 1/2 （pERK1/2） were also detected. Results Maternal hypoxia from day 3 to 21，or from day 9 to 21 of pregnancy induced increased expression levels of cardiac ACE and AngⅡ in male offspring at the age of 3 months （all P<0.05）. They also induced increased mRNA expression levels and protein levels of cardiac AT₁ in male offspring at the age of 3 months and 5 months （all P<0.05）. And they lead to decreased mRNA expression level and protein level of cardiac AT₂ in male offspring at the age of 5 months （all P<0.05）. But maternal hypoxia from day 15 to 21 affected the expression of AT₁ and AT₂ only in male offspring at the age of 5 months （all P<0.05）. Maternal hypoxia from day 9 to 21 lead to increased protein levels of cardiac pERK1/2 and increased mRNA expression levels collagenⅠand collagen Ⅲ（all P<0.05）. Maternal hypoxia from day 3 to 21 increased the expression of cardiac pERK1/2，collagenⅠmRNA and collagen Ⅲ mRNA （all P<0.05），but maternal hypoxia from day 15 to 21 didn’t affect the expression of cardiac pERK1/2，collagenⅠmRNA and collagen Ⅲ mRNA （all P>0.05）. Conclusions Hypoxia during pregnancy will lead to the activation of cardiac ACE-AngⅡ-AT1 axis in adult male offspring，which is most obvious when maternal hypoxia starts from day 9 to 21，or from day 9 to 21 of pregnancy，and will lead to the phosphorylation of ERK and cardiac collagen deposition.