An accurate active islanding detection method for grid-tied inverters in distributed generation using phase disturbance based on grid synchronisation is presented in this study. To have good performance on both power quality and islanding detection, a third-harmonic injection is generated by a new kind of phase disturbance and the scope of phase disturbance coefficient is precisely defined, besides, for extracting the third-harmonic component at the point of common coupling accurately, a selective harmonic extraction based on multiple second-order generalised integrators is also provided. Performances of the proposed method have been studied and confirmed through extensive simulations using MATLAB/Simulink platform.