Electron paramagnetic resonance (EPR) spectra of Cu2+doped lithium potassium sulphate (LP3) have been studied at different temperatures. The spin-Hamiltonian g and A parameters have been evaluated. Phase transitions in LP3 were observed at low temperature. The measured g-values indicate a rhombic field for Cu2+in the lattice at the temperature range 300–215 K. Between 215 K and 123 K an orthorhombic field suggested. The bonding parameter (∞2), Fermi-contact term (K) and the free ion dipolar term (P) are evaluated using the principal g and A values. The ground state were runction for Cu2+ion in (LPS) is determined.