Pnicogen bond (ZB) is a new kind of intermolecular weak interaction, which would be an important strategy for the construction of supramolecular materials. In this paper, ab initio MP2/aug-cc-pvDZ calculations have been carried out to characterize the X-P ⋯ O ZB interactions between HCHO and PH₂X (X=CH₃, H, C₆H₅, F, Cl, Br, and NO₂). The calculated interaction energies with basis set super-position error (BSSE) corrections in seven ZB complexes are between −7.51 and −20.36 kJ·mol⁻¹. The relative stabilities of the seven complexes increase in the order: HCHO⋯ PH₂CH₃ < HCHO⋯ PH₃ < HCHO⋯ PH₂ C₆H₅ < HCHO⋯ PH₂ Br < HCHO⋯ PH₂ Cl < HCHO⋯ PH₂F < HCHO⋯ PH₂NO₂. The natural bond orbital (NBO) and natural resonance theory (NRT) analysis were employed to investigate the electron behavior and nature of the ZBs. The natural bond orbital interactions in the ZBs are mainly LP^1,2 (O) → 𝜎* (P-X). The P-X (X= Br, Cl, F and NO₂) are more suitable for acting as ZB donors than the P-X (X=H, CH₃ and C₆H₅) groups. The electron density topology properties based on atoms-inmolecules (AIM) theory showed that the ZB interactions in the HCHO⋯ PH₂X (X=Br, Cl, F and NO₂) are stronger than those of HCHO⋯ PH₂ X(X=CH₃ , H and C₆H₅) complexes, indicating that the electron withdrawing of X benefits for the stability of ZB structure.