Aiming at the problem that electronic instruments need to maintain complete electrical isolation between the signal source and the signal processing when applying self-signal source signals to the electronic signal processing circuit, a transformer-coupled isolation amplifier is designed. In an isolated amplifier, the input signal is applied to the input winding of the transformer. The secondary winding of the isolation transformer is connected through a high-gain differential input terminal, providing negative feedback around the operational amplifier. The secondary winding of the transformer is connected to the negative input terminal of the amplifier. According to the virtual short principle of the operational amplifier, the voltage input at the negative terminal of the operational amplifier is driven to a very small value. The negative feedback from the operational amplifier generates current in the secondary of the transformer, which can basically counteract the magnetic flux produced by the current flowing in the primary, thereby reducing the influence of nonlinearity in the BH curve of the transformer. Test data results show that this transformer-coupled isolation amplifier has a high degree of linearity.