Abstract： Objective Choose the rat placenta which are similiar to human beings as the research objects, and choose vascular development as the breakthrough point. Give the rats folic acid through stomach with high dose, medium dose and small dose as intervention. Methods Choose the 13.5 day after fertilization as the time point, observe folic acid on the function of the placenta in situ and in the body. By oral administration of folic acid pregnancy to the rats, to observe the effect of folic acid intervention on placental blood vessels; detect placental VEGF, CD34 expression and FE3 of pregnant rats level. Results The folic could adjust the expression of VEGFand Ⅷ factor positively and negatively with affect cell proliferation, and promote the proliferation activity of the placenta of the pregnancy rats. Folic acid also promote the development of the placenta by improving the synthetic function of placenta. Conclusion Certain dose of folic acid is good for placental tissue structure and function.