Obiective To discuss the diagnosis value, limitations and mutual complement of MRI and TDUI in the fetus. Methods, TDUI and MRI was performed in 24 cases pregnant women that suspected fetus congenital malformation by Ultrasound examination, the examination results were compared by MR1 and TDUI with the clinical results.Results The 9 cases congenital malformation of 24 cases pregnant women were found by MRI. The 9 cases were confirmed and 3 cases were more sufficient by MRI. The one case examined by MRI was normal other than Ultrasound examination. Conclusion MRI is superior to Ultrasound in diagnosing malformation of nervous system. The Ultrasound and the TDUI in particular is better in finding the surface malformation than MRI. In clinical application, MRI and Ultrasound must be connected to make up the limitation and have a definite diagnosis.