When the distance of the main girders between parallel twin-separate bridges become small, the aerodynamic interference effect of twin-separate bridges has disadvantages influence on the flutter performance. In order to improve the flutter stability of long-span twin-separate bridge, some effective aerodynamic control measures were employed due to the poor aerodynamic performance of the deck form. A two-separate bridge with Π Shaped deck is taken as an example to conduct a series wind tunnel tests of section model, and the change laws of flutter critical wind speed and aerodynamic derivatives for twin-separate parallel bridges under many different aerodynamic measures including different spacing ratio, wind fairing, vertical stabilizing plate and horizontal splitting plate. Results showed that aerodynamic interference effect is harmful to the flutter stability of two-separate bridge, where the influences of aerodynamic interference effect on the windward deck are larger than those on leeward deck, and the effect on close deck are larger than those on open deck, as well as the effect decreases gradually as the spacing ratio increases. The bridges with the faring angle of 65 has the best flutter stability, and all the vertical stabilizing plates with the below quartile point and up central point can improve the flutter performance while horizontal splitting plate is adverse to the flutter performance.