[en] Kondo lattice heavy fermion system CeRuSn_3 exhibits anomalies in magnetic susceptibility and specific heat at a temperature T ≈ 0.6 K (much lower than the average Kondo temperature T_K ≈ 3.1 K) which are thought to be related to antiferromagnetic ordering or spin-glass transition. Our muon spin relaxation (μSR) data show no clear evidence of long range magnetic order in CeRuSn_3 down to 84 mK. However, it reveals a slowing down of spin fluctuations below 0.6 K, and a glassy spin-dynamics seems more appropriate. The inelastic neutron scattering data reveal broad excitations around 6-8 meV due to the crystal field effect