Abstract: To achieve the best sub-array dividing solution for digital microfluidic biochip,The test process was modeled,and test cost that measured by test time and the number of test droplets is proposed in this paper.The test cost is analysed by the tools of MATLAB,and some important discoveries are achieved.The first is that with the increasing of the number of sub-arrays divided,the test cost will rise at first,and then go down,and the number of sub-arrays divided corresponding the lowest cost is selected as the best sub-array dividing solution for parallel testing.In addition,test cost will rise with test time proportion increasing,and decease with the number of test droplets raising while the number of sub-arrays divided less than the best sub-arrays divided numbers.On the other hand,when the number of sum-arrays divided more than the best sub-arrays divided numbers,test cost decrease with test time proportion increasing,and rise with the proportion of the test droplets number raising.