The flow characteristic of flat gate valves with a diversion hole is equal to that of pipelines of thesame specification. The characteristic is shown in per centum form. As for valves without a diversion hole, its cavity fly span is smaller than that of wedge gate vales and it is a regular cylindrical object, therefore. characteristics of the valves are similar except that they have a larger pressure loss. Besides, their flux adjustment behavior is better than that of the ones with a deversion hole.