<p>Quantum secure direct communication (QSDC) provides unconditional security for direct information transmission without the need for pre-shared keys. However, practical implementations using weak coherent pulse (WCP) sources face critical challenges from device imperfections, such as emitting vacuum and multiphoton states. Here, we introduce a heralded QSDC protocol leveraging squeezed-state superposition in a cross-Kerr nonlinear medium, where single-mode squeezed states interfere with coherent states to generate superposition states via post-measurement selection. We perform numerical simulations and parameter optimization to achieve the optimal secrecy message transmission rate for each channel attenuation. At shorter transmission distances, our protocol is slightly less efficient than those based on WCP. However, as the distance increases, it shows a significant advantage in secrecy message capacity. Compared to the DL04 protocol using spontaneous parametric down-conversion (SPDC) sources, our protocol achieves comparable secrecy message capacity under ideal single-photon detection. Under conditions of low channel attenuation, this protocol achieves a lower secrecy message transmission rate when compared to SPDC-based protocols. However, under high attenuation conditions, its transmission rate is higher due to the effective suppression of multiphoton contributions in practical single-photon detectors. At 7 dB attenuation, the secrecy message transmission rate of this protocol is 1.62 times that of SPDC-based protocols. This work establishes a robust framework for high-capacity, long-distance quantum secure communication systems.</p>