We experimentally analyze the performance of Schottky mixer-based THz receiver in a high-speed THz wireless transmission system incorporating an ultra-broadband uni-travelling carrier photodiode (UTC-PD) as photo-mixing emitter. The multi-channel photonic THz wireless system operates in the 375–450 GHz band with 4×10 GBaud/s QPSK modulation, reaching an overall capacity of 80 Gbit/s. The bit error rate (BER) performance for all the channels reaches below the forward error correction (FEC) threshold of 3.8∗10−3, and the experimental results indicate that the existence of harmonics spurs in the receiver however severely affects the receiver bandwidth and induces the performance degradation of THz wireless communication systems.