This paper reports on the study of the Stark effect on the magnesium photoionization spectrum near its first ionization threshold. The threshold had a red shift amount proportional to the square root of the applied electric field strength. Modulation of the oscillator strength beyond the ionization threshold was observed, and can be attributed to the field induced resonances. A tunneling effect was evident in the spectrum. Level anti-crossing between components of the neighboring Stark manifold was also observed in this study.