The initiation of translation is very important in the process of protein synthesis. On the major eukaryotic mRNAs template,initiation of translation is completed by a capdependent mechanism. Recent works demonstrate:a set of animal viruses mRNAs appear to have a different initiation mode based on a cap-independent internal initiation mechamsm.These mRNAs contain some conserved secondary structure in 5′untranslated region.Some specific protein factors can stimulate translation through the conserved site.