Experimental investigation has been carried out concerning acetaldehyde oxidation with oxygen/air using homogenous catalyst mangan acetate. Two steps of work have been carried out. Firstly, hydrodynamic of reactor has been evaluated by measuring gas-liquid mass transfer coefficient using oxygenation dynamic method. This work gave empirical correlation of the coefficient in term of rotation speed and gas flow rate. Secondly, the evaluation of acetaldehyde oxidation reaction was carried out in mechanically agitated reactor at atmospheric pressure, where impeller rotation speed, air flow-rate, and temperature were varied. This research showed that increasing impeller rotation speed could not increase acetaldehyde conversion. On the other hand, the selectivity of acetic acid decreased with increasing impeller rotation speed. The observation also showed that the conversion of acetaldehyde and selectivity of acetic acid increased with the increasing of gas flow rate and temperature. The maximum conversion was 32.5 % and the highest selectivity was 70.5 %.