Abstract: The polymorphism of Short Tandem Repeat(STR) have been used in individual identifications,especially in medicolegal investigations.But such technologies are too expensive to be preformed widely.The 4 bp repeats unit STR site which was used commonly in medicolegal investigation were chosen to design the new PCR system to limit the PCR products length as 4 bp multiple and less then 160 bp,a Mini STR technique,and optimized the PAGE conditions to distinguish the single STR repeat unit accurately.Then the number of STR repeat units can be measured the numbers of the integer multiple alleles accurately and easily by using 8bp DNA ladder.The new methods preformed in analyze of polymorphism of STR,a simpler and cheaper methods,is suitable to make human gene identification card(ID-card) and it is possible that each people hold a gene ID-card.