Abstract: A complex mechanical seal for vertical multiple stage pump includes a hollow cylinder fixed plate positioned in the vertical multiple stage pump. It is coupled to a fixed barrel. The bottom hole of fixed barrel is used as the passage of pump axle. A long axle bushing in the inner part of the fixed plate is fixed on the pump axle. A balance plate is positioned below long axle bushing. The circumference of balance plate has a flange. The mechanical seal is fixed on the upper space of the balance plate and fixed on long axle bushing. A return water passage is connected to the upper part of balance plate and to inlet of pump, and the high pressure region. A and low pressure region B, are needed as the pushing force. The complex structure of balance plate and mechanical seal is simultaneously easier and quicker to assemble and disassemble.