Based on the density functional theory (DFT), the structural, electronic, optical, magneto-optical and thermoelectric properties of KCaN$_2$-K, KCaN$_2$-Ca, KCaN$_2$-N Heuslerenes have been discussed. Energy changes in the volume of these compounds indicate the presence of their ground-state points. These three structures, KCaN$_2$-K, KCaN$_2$-Ca and KCaN2-N have magnetic moments 3.0, 3.0 and 1.0μB. The electronic results indicated that the KCaN2-K Heuslerene is a magnetic semiconductor and the other two are half-metallic with 100% spinpolarisation. Optical studies showed that in both directions of the incident light (along the x- and z-axes), these compounds have semiconductor behaviour.The highest light response occurs inKCaN2-K Heuslerene at the visible edge.KCaN2-Ca and KCaN$_2$-N Heuslerenes have the lowest optical energy loss function in the IR and visible regions. Also, magnetic behaviour of the KCaN$_2$-K, KCaN$_2$-Ca and KCaN2-N Heuslerenes causes a magnetic response tolight in theUVedge region and at higher energies to control the Kerr angle rotation and magnetic polarisation of light.