Scintillation induced by atmospheric turbulence is an important factor affecting the performance of terahertz wireless communication system. A space diversity scheme is proposed to improve the performance of terahertz photon-counting wireless communication system which is influenced by strong atmospheric turbulence and noise. The Bit Error Rate(BER) expression of transmit diversity system, receive diversity system and Multiple-Input Multiple-Output(MIMO) system in strong turbulence channel are respectively derived. The numerical simulation results show that spatial diversity techniques which can be used to antagonize strong atmospheric turbulence effectively and reduce the BER of the communication system, is a simple and effective approach to improve terahertz wireless communication under adverse weather conditions.