Using the light-assisted-collisions (LAC) and the feedback controlling loop on a quadrupole magnetic field, we have realized high probability of single atoms in the far-off-resonance trap (FORT). We analyzed the principle of LAC irradiated by a red-detuning laser or by a blue-detuning laser. And we also experimentally proved that using the red-detuned laser (the blue-detuned laser) we can realize 50% (80%) of single atom probability in the FORT. Using the feedback controlling loop, we realized 95% of single atom probability in the FORT, which opens a way for a two-dimensional FORT array. When the number of atom was zero, we decreased the gradient of the quadrupole magnetic field to quickly load atoms, and when we had more than one atom in the FORT, we switched on the blue-detuned laser to irradiate the atoms to play LAC. We measured the second-order coherence degree of the fluorescence photons emitted by the atom trapped in the FORT by using HBT scheme and found it was g(2)(τ=0)=0.08.