Abstract: Micro-titration technique was applied to the determination of dissolved oxygen (DO) in water by the conventional iodometric method.WD-CO3 microtitrator (3.000 mL) was used in the experiments.A self-made precise micro-pipet,giving an accuracy to 0.001 mL,was used for transfering of standard solution and sample solution.A comparative study of the method by microtitration and by macrotitration was made,and the results showed the data obtained by both method were in good consistency.The values of standard deviation and relative standard deviation were tolerable as required by quantitative analysis.The feasibility of the microtitration of dissolved oxygen in water was verified.