In the study of miniature optically pumped NH3 FIR laser, We found that, when the NH3 gas was pumped by CO29R(16) IR laser, the 90 gm FIR laser line would be obtained with high efficiency. Especielly, in case the length of sample tube is very short for mini-OPFIRL, and the operating gas pressure will be several tens Torrs. So that the pressure broadening was important. In the CO29R(16) pumped NH3 s-aP(7,0) and s-an41) FIR lasers, the lasing frequency of these two transitions are close to each other as shown in Fig. 1 and Fig. 2. So the pressure broadening course part of these laser lines overlap to each other. The 6Ki0 transitions in the molecular system as shown in Fig. 3 are for- bidden, so overlaping of spectral line can only increace the background intensity of the FIR signal, and the FIR laser will be enhanced as shown in Fig. 3. The efficiency of the system will be much increased. We call it the two photon processes interaction enhancement effect.