This application provides a terminal antenna and a mobile terminal device. The terminal antenna includes a frame, a first feed, and a second feed. A first gap and a second gap that partition the frame are provided on the frame, to form a first conductor, a second conductor, and a third conductor. A part of the frame on a side of the first gap away from the second gap forms the first conductor, a part of the frame on a side of the second gap away from the first gap forms the second conductor, and the frame between the first gap and the second gap forms the third conductor. The first feed is electrically connected to the first conductor, so that the first conductor radiates a signal, and the second feed is electrically connected to the second conductor, so that the second conductor radiates a signal in a low band. The terminal antenna further includes a control circuit. One end of the control circuit is grounded, and the other end is electrically connected to the first conductor, to control the first conductor to radiate a signal in a medium-high band or radiate a signal in the low band. The terminal antenna can operate in 4G and 5G low bands, and has good mobile communication performance.