In order to improve communication efficiency, applying THz communication to MHNs is envisioned as a promising approach. However, the security of THz MHNs is rarely discussed and urgently needs attention. For the purpose of effectively resolving the exposed security issues in THz MHNs, in this article, an intelligent spectrum control strategy in a THz network is proposed, and an intelligent spectrum control sequence is generated, which has the characteristics of adaptive frequency slot number, wide gap, and orthogonality. Extensive theoretical analyses prove that this sequence outperforms the sequences available in uniformity, randomness, and Hamming correlation. Simulation results indicate that the proposed strategy has great anti-attack capability and high throughput, and that the BER of THz communication with the proposed strategy can be increased two orders of magnitude in a complex electromagnetic environment. By using the proposed strategy, the security and reliability of future THz MHNs can be ensured.