Ground states of BrCl in different electric fields from 0 to 0.035 a.u. are optimized by HF(Hartree-Fock) theory at 6-31+G(d,p) basis sets. Optimized parameters, dipole moment, total energy, bond length, charge distribution, the highest occupied molecular orbital energies, the lowest unoccupied molecular orbital energies, energy gap, infrared spectrum and dissociation potential energy surface(PES) are obtained. It shows that with increasing external field from 0 to 0.035 a.u. along molecular axis Z (Br-Cl bond direction), molecular total energy increasing firstly, then decreasing, while bond length and dipole moment decreases at beginning and then increases. Energy gap decreases and atomic charge distribution increases with increasing electric field. IR vibration spectrum of BrCl molecule shows an observable blue shift firstly and then red shift with increasing of external electric field. External electric field of 0.045 a.u. is enough to induce degradation of BrCl with Br-Cl bond breaking. It provides reference for degradation of BrCl in external electric field.