Measuring complex Internet topology is primary research activities in Internet-related research fields and has become a focus recently. And due to the complexity of Internet topology, further processing is required and is thoroughly studied in this paper. First, Internet topology measurement is performed by CAIDA measurement approach with more than twenty monitors. Then the problem of sampling bias is quantitatively studied. Mathematical models are introduced into both the node bias problem and link bias problem, and final option is gained. Final results are that more than 156 CAIDA monitors are necessary in order to have a full Internet topology measurement result.