The loss characteristics of the low-frequency terahertz band (0.325THz-0.50 THz) were tracked during sample aging from perspective of loss tangent, amplitude and phase. The attenuation of signal not only increases with the frequency but also with the aging time. Phase decrease with frequency and is also related to aging time. But the change of rate is almost same for all samples. Besides, it is observed that the loss tangent increases with the frequency, which will also increase with the aging time. Thus, investigators may get a deep understanding of rubber’s remaining life by analyzing optical parameter in terahertz range.