In order to make full use of the advantages of microwave photon frequency doubling and simplify the system complexity, a scheme of broadband terahertz vector signal generation and fiber transmission based on dual-parallel Mach-Zehnder modulator (DPMZM) and uni-traveling-carrier photodiode (UTC-PD) is proposed in this paper. A vector signal is modulated in the positive third-order sideband of the light wave, and the local oscillator signal is modulated in the negative third-order sideband of the light wave. The scheme is simulated and verified by VPI software. The simulation results show that when the system adopts six times the frequency of 36.7 GHz local oscillator signal, a terahertz vector signal with orthogonal phase shift keying with carrier frequency of 220 GHz and code rate of 20 GSym/s is generated. After 1-4 km optical fiber transmission, the power loss of the receiver is less than 3 dBm.