Abstract: Aphid is a group of small insects in the Homoptera.There are approximately 4 000 aphid species all over the world.Many of them attack important agricultural crops and therefore have economic importance.However,some species such as Chinese gallnut aphids are beneficial for human beings.Most aphids display complex life cycles with alternation of sexual and asexual generations and host plant alternation.Molecular genetic markers have good stabilities,high variability and mostly are free from environmental influences.So they were very suitable for aphid research and could tackle some problems which the traditional taxonomical methods could not solve.The paper introduced a simple and effective method that could extract genomic DNA from a single aphid individual and could be used for the research of molecular genetic marker such as RAPD,RFLP and DNA sequence determination.