Stark frequenoy shift for the CH3F optically pumped far infrared laser light has been theoertically calculated.It is pointed out that there is the possibility of resonance between the methylfluoride emmited far infrared laser line (496 μm) and 3P0→3P1 transition in Mg atomio beam at the electric field intensitry of 2.9×104～4.4×104 v/cm,meanwhile maintaining resonance between the laser levels of methylfluoride and the CO2 pumped line 9p(20).It has been predicted that there are four sets of possible operating transitions:QR(11,5,-11),QQ(12, 5,-11);QR(11,6,-6),QQ(12,6,-6);QR (11,7,-3),QQ (12,7,-3) and QR(11,8,0),QQ(12,8,0).