The EPR spectrum of a low dimensional antiferromagnet Mn[C10H6(OH)(COO - )]2×2H2O investigation was performed in the frequency range 9.6 GHz. In H||h polarisation in ab plane along with a basic magnetic resonance line in field H0 an additional absorption line with of relatively low intensity in resonant field Н0/2. The peak intensity of the observed line is of the order of 1/800 less then the peak intensity of the basic EPR line in H⊥h polarisation. The availability of an additional absorption line is due to low dimensionality of the system. The angular and frequency dependences of the fundamental absorption line in the EPR spectrum of the antiferromagnet Mn[C10H6(OH)(COO - )]2×2H2O was studied. The EPR spectrum behaviour at high temperatures is described by the diffusion model for quasi-two-dimensional magnetic structures. The diffusion constant D =6.2×10 11 sec -1 , the starting time 1 τ ∼1.5×10 -12 sec and the end time of the diffusion process 2 τ ∼8.8×10 -10 sec was estimated. A non diffuse contribution in the line width of EPR spectrum was determinate.