The invention relates to an improvement of a speed reduction mechanism of an agricultural machine. The speed reduction mechanism comprises a reducer box and a ventilation component. The reducer box is internally provided with a worm, a worm wheel connected to the worm, an accommodating space and a first pressure relief channel. And a second pressure relief passage communicating with the first pressure relief passage, the second pressure relief passage is inclined at an angle relative to the first pressure relief passage； the ventilation member includes a vent pipe connected to the reducer tank and a a hose having a first straight pipe section, a bent section and a second straight pipe section, the vent pipe is connected to the reducer case by the first straight pipe section to communicate with the first pressure relief passage, the bend The segment is an arc-shaped bent structure and is respectively connected to the first straight pipe segment and the second straight pipe segment, and the end of the second straight pipe segment is connected to the hose； wherein the inner diameter of the tubular body of the hose is smaller than the pipe of the vent pipe Body diameter. Thereby, the problem of poor lubrication of the lubricating oil inside the gearbox is improved, resulting in fuel injection problems, and the safety and durability of the operating tool are improved.一種農用機械之減速機構改良，該減速機構包括一減速器箱以及一通氣部件，該減速器箱內部設有一蝸桿、與該蝸桿相接的一蝸輪、一容置空間、一第一釋壓通道及與該第一釋壓通道連通的一第二釋壓通道，該第二釋壓通道相對於該第一釋壓通道呈一傾斜角度；該通氣部件包含連接該減速器箱的一通氣管及一軟管，該通氣管具有一第一直管段、一彎折段及一第二直管段，該通氣管以該第一直管段連接該減速器箱以連通該第一釋壓通道，該彎折段為一弧狀彎折結構並且分別連接該第一直管段與該第二直管段，該第二直管段的末端組接該軟管；其中該軟管的管體內徑小於該通氣管的管體內徑。藉此，改善減速箱內部潤滑油循環不良問題而導致噴油的問題，並且提升操作機具時的安全性與耐用性。
