Abstract: Vegetable production and horticulture are rising as an important industry in China. A large amount of vegetable waste and flower straw needs to be treated properly. Composting is potent to recycling organic waste. The effect of ventilation rate on vegetable waste and flower straw co-composting on pilot scale was investigated. The mixture of shredded vegetable waste and flower straw was composted in 2 m³ static aerobic bed with three level ventilation rates (0.005, 0.0075 and 0.01 m³/(kgVS·h)). Of these compounds, temperature, organic matter, moisture content, pH value and volume of mixture were measured during composting. Temperature of mixture could come up to 60℃ and maintain beyond three days. Especially, when the ventilation rate was 0.01 m³/(kgVS·h), temperature of mixture exceeded 80℃, what was named as super high temperature, from the second day to the fifth day, this phenomenon was unusual during composting. Among three level ventilation rates, the high rate had rapid degradation of biological organic matter, and the more temperature rose, the more organic matter disappeared. It was unfavorable for degradation at the latter of composting because of too much loss of water. Of all the three ventilation rates, moisture content and pH value of mixture had the same trend and no obvious difference, moisture content was declined and pH value was increased. Three volumes of mixtures were reduced to about half of initiation also in the first five days composting, and the highest reduction occurred on the ventilation rate of 0.01 m³/(kgVS·h).