Abstract: This article essentially describes automatic opto-electronic measuring system of logs. The system consists of two units: diameter measuring unit and length measuring unit. The diameter measuring unit is composed of parabolic type laser scanner, synchronizing part and photoelectric detectors with optical fibre as light transmission path. The length measuring unit comprehends length measuring disc and passing log sensor. The operation principle is discussed and then the circuit of input signal control, data processing and output display are presented. The system can be used on automatic production lines of timber storage yards, timber mills etc. Measuring range of logs: diameter 14-80cm; Length 2-8m.