Objective From the perspective of making full use of database comparison function, giving certain guidelines to analyze mixed DNA profile,compare database,screen comparison results. Methods Using CPI to describe the identification of mixed DNA profile.Using CPBI to estimate reliability of individual samples being included. Results When CPI is less than 10-7, mixed DNA Profile is worth to be compared in database.When the number of alleles at one locus is more than 2, retain an additional allele will not reduce identification too much. According to the CPBI of the included samples,we can find the most reliable sample.