A local coil and a magnetic resonance imaging system are provided. The local coil includes an antenna part, an adjustment part and a transmission part. The antenna part includes a first capacitor connected in series for adjusting a frequency of the antenna part. The adjustment part includes a tuning/detuning diode and is connected in parallel to the first capacitor, and the tuning/detuning diode is used for adjusting tuning and detuning of the antenna part. The transmission part includes a radio-frequency transmission line that connects the antenna part and the adjustment part, and the transmission part provides a phase difference of an odd multiple of 180° between the antenna part and the tuning/detuning diode.