In investigating the variation of nonstationary wavelets in a medium with attenuation, we apply the 45-degree wave equation to wavefield upward continuation with a constant-Q model. The amplitude variation and phase property of the propagating wavelet are simulated and then validated by the spectral ratio and spiking deconvolution approach. The synthetic data are also compared to the forward-Q- filtered trace which is generated by another method. The estimated Q value from synthetic data by the spectral ratio method is quite close to the Q value given in the model. The result of spiking deconvolution shows the wavelet in the synthetic data is effectively minimum phase. A layered-Q model is also tested. The average Q estimated by spectral ratio method is reliable for the noise free data.