The ability to synthesize RNA in the laboratory is critical to many techniques in Biomedical Science. In this study, two techniques ofin vitro transcription were applied using the T7 functional sequence of cloned plasmid and attaching this functional sequence as well as a poly T tail to the 5 primes of specific primers for direct in vitro transcription in order to prepare, from a small volume of RNA extracted from clinical samples/viruses, in large scale RNA positive controls of Influenza A, B, C (FluA, FluB, Flue), hRSV, hMPV, SARS, and the Seg 7,4, 6 (M, HA, NA) of Avian Influenza A/H5Nl. RNAs prepared by this method was pure, homogenous with the yield of about 10 exponent 13 copies per 20ul reaction.