Observations of interplanetary slow shocks near 1 AU are rare. From the magnetic field data obtained from MFI and the proton and electron data obtained from SWE of the WIND spacecraft, we identify the observation of a reverse slow shock on December 24, 1994. The plasma β is small in preshock region. A new method is introduced to determine the best‐fit solutions for both the normal of the shock surface and the coplanarity plane when the total deviation of the observed magnetic field and velocity vectors from the theory reaches a minimum. The flow conditions on both sides of the slow shock agree well with those predicted by MHD shock theory.