Abstract: Relationship between the solar wind-magnetosphere energy coupling function and the energy consumption in the magnetospheric system is tested by the samples during period of northward B_z(>10 nT) of IMF. It is shown that the energy function which can well describe the solar wind-magnetosphere coupling when B_z>0 is no more applicable for B_z>10 nT, but the coupling still exists, the effects of which are mainly found at the polar cap. Dst often turns to positive when B_z> 10 nTand the coupling mechanism is different from that when B_z<0. New coupling function has to be introduced to describe the solar wind-magnetosphere coupling for the case of B_z> 10 nT.