Analysis with oxygen monitoring system on the variation of oxygen concentration at different stages of pig manure composting showed that in a short time after ventilation at different composting stages, the oxygen concentration increased by 17% or more, and the oxygen consumption rate at temperature increasing stage and at the beginning of high temperature stage could reach up to more than 900 microl x L(-1) x s(-1), while decreased at the stages of high temperature and of dehydration as the composting process going on. The oxygen consumption rate decreased to lower than 100 microl x L(-1) x s(-1) after 5-7 days at the stage of high temperature. A ventilation strategy was proposed based on the analyses.