To facilitate the designing process for vector-based siRNA and siRNA cassette, a tool set has been developed consisting of a siRNA target finder, a siRNA construct builder and a siRNA sequence scrambler. The siRNA target finder is used to identify candidate siRNA target sites. The program automates homology filtering, minimizes non-specific cross-reaction, filters target sites based on RNA duplex internal stability and siRNA sense/anti-sense strand secondary structure. The siRNA construct builder is used to create a siRNA hairpin construct as a vector insert or a cassette insert. The siRNA sequence scrambler is used to generate a negative control sequence for siRNA experiments. Together, these programs provide a comprehensive utility set to address the specific bioinformatics need of DNA-based siRNA design.