Sounding rod control method for blast furnace

The invention relates to a sounding rod control method for a blast furnace. The sounding rod control method comprises the following steps: an on-site absolute value encoder for a sounding rod sends a rod pay-off distance to a decoder of a sounding rod detector; the decoder converts a transmitted pulse signal into a BCD code, and a PLC converts the BCD code into a value and displays the value on a center control picture; when the sounding rod just drops down, a master controller changes a pay-off speed reduction point and a stockline site into center control changeable value points; when the sounding rod reaches the pay-off speed reduction point, a sounding rod frequency converter reduces the sounding rod pay-off speed; when the sounding rod reaches the stockline site, the sounding rod frequency converter reduces the sounding rod pay-off speed; and when reaching a material surface, the sounding rod starts to track the material surface, wherein when the sounding rod reaches the pay-off speed reduction point, fo