  We present emission maps (1.5'$\times$1.5' scale, corresponding to 0.18 pc)
of the DCN ($J=2-1$) and DCO$^+$ ($J=2-1$) lines in the 2 mm band toward the
Orion KL region obtained with the 2 mm receiver system named B4R installed on
the Large Millimeter Telescope (LMT). The DCN emission shows a peak at the
Orion KL hot core position, whereas no DCO$^+$ emission has been detected
there. The DCO$^+$ emission shows enhancement at the west side of the hot core,
which is well shielded from the UV radiation from OB massive stars in the
Trapezium cluster. We have derived the abundance ratio of DCN/DCO$^+$ at three
representative positions where both species have been detected. The gas
components with $V_{\rm {LSR}} \approx 7.5-8.7$ km/s are associated with low
abundance ratios of $\sim4-6$, whereas much higher abundance ratios
($\sim22-30$) are derived for the gas components with $V_{\rm {LSR}} \approx
9.2-11.6$ km/s. We have compared the observed abundance ratio to our chemical
models and found that the observed differences in the DCN/DCO$^+$ abundance
ratios are explained by different densities.
