^{Geo-membrane welder is a new welding machine which is developed by our company. They can weld geo-membrane of various thickness and are applicable for welding of all thermal-fused material such as LDPE, PVC, HDPE, EVA, PP and PVC,HDPE,EVA,PP The control of this series adopt PID automatic thermostatic control with high control and ow temperature fluctuation. Speed control of this series adopt PWM automatic voltage and regulation speed circuit.Direct current servo the motor drive with great output torque and staple performance in walking. It can maintain a constant speed on the condition of creeping, vertical creeping and road load. Also this series of welding machine are stable in performance despite of external temperature and voltage variation. This series of welding machine is excellent in performance and easy for operating, with high welding speed and good work quality. It is extensively used in engineering projects such as expressways, tunnels, reservoirs, waterproof of construction and so on.}