The formation mechanism of drawing‐inducedE’centers in silica optical fibers is clarified by analyzing the thermodynamic behavior of point defects during the drawing process. TheE’center concentration in the fibers is given bynd=np exp(−Ef/kTd−A/V1), whereTdis the drawing temperature,V1the drawing speed, andAa constant. The formation energyEfis 3.8 eV while the precursor concentrationnpis 7×1022g−1. TheE’center concentration at the fiber surface is greater than that at the center because of the transverse difference in the quenching rate during the drawing process. The annealing behavior of theE’center concentration is expressed asnd(t)=nd(0)exp[−&ngr;t exp(−Ed/kTa)], whereTais the annealing temperature. The activation energy for the motion of theE’centersEdis 0.2 eV while the frequency factor &ngr; is 8×10−3sec.−1.