The invention provides an interconnected network primary frequency response capability evaluation method under ultrahigh voltage and high power deficiency. The method comprises the following steps ofA, building a thermal power generating unit frequency response simulation model; B, building a call wire module simulation model; C, building a simulation model of a two-region interconnected network;D, constructing an interconnected network dynamic frequency response capability evaluation index. According to the interconnected network primary frequency response capability evaluation method underthe ultrahigh voltage and high power deficiency, the new thermal power generating unit frequency response simulation model and the call wire model are utilized to build the simulation model of the two-region interconnected network, and on the basis of the simulation model of the two-region interconnected network, a primary frequency modulation capability index of the power generating unit in theinterconnected network is defined, and can be precisely calculated through primary frequency modulation power, frequency deviation and unit frequency modulation power, so that the primary frequency response capability of the power generating unit is evaluated.