Transient noise simulations are beneficial to design analog circuits, such as peak detection circuits for detecting very small signal levels, or circuits having large gains to be saturated by noise signals. Though the noise characteristics of these circuits can be simulated with SPICE in frequency domain, the dynamic noise performance cannot be shown with noise analysis in frequency domain. The transient noise model for white noise such as thermal noise of the resistor can be generated in time domain with Gaussian distributed random numbers, because the white noise is independent of frequency. But the transient noise model for frequency-dependent noise sources such as 1/f noise is hard to generate in the time domain. In this paper, a transient noise model for frequency-dependent noise sources is presented, and its application is shown.