The invention discloses a low-temperature C-waveband wide-temperature region broadband microwave isolator, which comprises ferrite, wherein the ferrite is made of YCaAlSnIG; and the YCaAlSnIG material comprises the following main components in mass percent: 50.1% of Y2O3, 39.7% of Fe2O3, 4.99% of SnO2, 2.45% of Al2O3 and 1.29% of CaO. According to the isolator disclosed by the invention, the relative operation bandwidth at low temperature of 4K-120K is greater than 66%; the isolating degree is high; the insertion loss is low; and the requirements of a superconducting receiver system on the low-temperature isolator can be met.