In order to guarantee the physical layer security of the transform domain communication system (TDCS)， a security-enhanced scheme based on 4-Weighted-type Fractional Fourier Transform (4-WFRFT) and artificial noise insertion was proposed. Firstly, the 4-WFRFT was applied to TDCS instead of the Discrete Fourier Transform (DFT) and Inverse Discrete Fourier Transform (IDFT), which maintained the system complexity while made the distribution of TDCS signals change in the complex plane. And then the artificial noise is inserted to further enhance the security. The expression of the Bit Error Rate(BER) and the security capacity for eavesdroppper were obtained. Simulation results show that whether with or without spectrum mismatch, the BER for eavesdropper kept 0.5 and the security capacity is positive when in the range of [0, 0.8) or (1.7, 4] in the security-enhanced TDCS. It provides a promising solution to extend the application of TDCS scheme where secure communication is required.
