The utility model discloses an isolation transformer for a solar inversion grid connecting device, which comprises a transformer body. The transformer body comprises an iron core (4) and high and low voltage windings (7) outside the iron core (4); the iron core (4) is made of an amorphous alloy material; the cross section of the iron core is rectangular; the high and low voltage windings (7) comprise a high voltage winding and a low voltage winding; the wound cross sections of the high voltage winding and the low voltage winding are both rectangular; and the low voltage winding and the high voltage winding are concentrically sleeved and wound on the iron core (4) from inside to outside. By using the transformer, the dead time loss of the transformer can be greatly decreased. Therefore, the output efficiency of a power supply system of the solar inversion gird connecting device can be improved obviously.