•Viscoelasticity of mixed systems dominated by cationic Gemini surfactant was studied.•Micelle length is very sensitive to small addition of anionic surfactants.•Hydrophobic part of anionic surfactants plays an important role.The viscoelasticity of a cationic Gemini surfactant, 2-hydroxyl-propanediyl-α,ω-bis (dimethyldodecylammonium bromide), abbreviated as 12-3(OH)-12, solutions at a total concentration of 80 mmol L−1 in the presence of small amount of anionic surfactant, sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS) and sodium laurate (NaL), respectively, were investigated by steady state and dynamic rheological measurements, and the relationships between the solution properties and the microstructure of wormlike micelles were analyzed. It is found that the addition of small amount of anionic surfactants has a tremendous effect on the viscoelasticity of 12-3(OH)-12 solutions, with the rheological behavior mainly affected by the structure of the hydrophobic part of anionic surfactants and highly sensitive to the interaction manner of the anionic additives with the cationic aggregates, which is one of peculiarities of Gemini surfactants.The viscoelasticity of cationic Gemini surfactant solution shows high sensitivity to the added small amount of anionic surfactants.