Because magnetospheric and ionospheric current source modelling is a prior step of global mantle conductivity imaging,we research on the current source modelling method and compare the C-responses excited by different sources. The study deduces a toroidal current source from time-varying geomagnetic fields with the IGRF-13 model and Green's function. Then we calculate the C-responses using the integral function method and verify the method on a layered Earth model. In quasi-dipole coordinate system,we compute the C-responses on the surface of the "1D+thin sheet" Earth model separately inspired by the toroidal current and its Y₁⁰ degree component,namely C_toro and C_Y1⁰ values,and compare them with the real values on the geomagnetic observatories. The outcome shows that ocean effect causes more disturbance on the real part of C_1d than its imaginary part and the source is mainly composed of its first-order part. At the GZH,QZH,and SSH observatories along the coastline,real part of C_toro is closer to C_real in around the period of 1~30 days,and real part of C_Y1⁰ is nearer in around the period of 30~100 days. Therefore,the local current may have a deep effect on the C-responses,its characteristics change with frequencies and it's influence may be evaluated carefully before GDS inversion.