Unique newly developed protective agent is non-toxic, It can fix the blood cells, restrain DNAse outside the cells, Prevent the genome DNA release. Protect the dissociative DNA to be degraded. It can supply better solution for researching and applying of the dissociative Plasma DNA. It can be applied for Noninvasive screening of fetal birth defects(Noninvasive Down syndrome detection), tumour finding and research，The progress of tumour treatment and curative effect assessment. Molecular diagnostic and inspection of acute disease. Clinical Drug development and testing.The dissociative DNA can be stored at temperature of at least 14 days. Which makes sample collection, transportation and storage more convenient.