Which type of grain is the best for 6 months old?

Try to only introduce grains to baby after 1 years. I know it's not the usual Chinese custom, but grains is not great for baby. In order to digest grains, your body needs to make use of an enzyme called amylase. Amylase is the enzyme responsible for splitting starches. And, babies don’t make amylase in large enough quantities to digest grains until after they are a year old at the earliest. Sometimes it can take up to two years.