1.High modularization design: may equip with various motor or other power input conveniently. Same machine type may equip with various power motor. It is easy to realize the combination and junction between every machine type. 2.Transmission ratio: fine division, wide scope. The combined machine type may form very large transmission ratio, i.e. output very low rotary speed. 3.Form of installation: the position to be installed is not limited. 4.High strength, the box body is made of high strength cast iron. Gear and gear shaft adapts the gas carbonization, quenching and fine grinding process, therefore the bearing capacity of unit volume is high. 5.Long life: Under the condition of correct type chosen (including choosing suitable operation parameters) normal operation and maintenance, the life of main parts of speed reducer (except wearing parts) should not be less than 20000 hours. The wearing parts include lubricating oil, oil seal and bearing. 6.Low noise: because main parts of speed reducer are processed, assembled and tested critically, therefore the noise of speed reducer is low. 7.High efficiency: the efficiency of single machine is not less than 95%. 8.May bear larger radial load. 9.It may bear the axial load that is not more than 15% of radial force. S series pair of level helical gear- worm reduction gear has big transmission ratios in worm gear level , working noise is extremely low.