In this paper, THz channel propagation characterization and modeling for a desktop environment is presented. Path loss and PDPs measured on the motherboard in both free-space and desktop resemble metal cavity are compared. To characterize the large scale fading of the channel, mean path loss model as a function of antenna height is proposed by treating the motherboard desktop environment as a partially dielectric filled resonant cavity. Good match between the measured and modeled path loss proves the model validity. For the shadowing across the frequency, Gamma-mixture model is applied to characterize the oscillations of in-cavity measured path loss. Results show that with proper choice of the number of mixed Gamma distributions $k$, the goodness of fit between the model and the probability density function (PDF) of path loss oscillations can reach more than 97\%. Multipath components are characterized by cluster-based channel modeling. Modifications were made on the conventional S-V model to accurately characterize the channel by rewriting the cluster power decay with step-wise functions and each sub-function is expressed exponentially in dB, and the ray power decay with power law approach. A good agreement can be observed between the model and the measurements.