A complete bearing-sealed root vacuum pump system capable of promoting vacuum ability of a condenser of a power plant provides a complete bearing-sealed structure. All chambers are isolated effectively so that liquid cannot flow there between and thus not to destroy the root vacuum pump. Therefore, the lifetime of the root vacuum pump is prolonged. The heat exchangers are arranged between the root vacuum pumps and the front stage pump so as to return the condensed water. The condenser vacuum is improved and thus the power generation efficiency is promoted, and power consumption is lowered. As a result a large power plant can save several thousand tons of coals per year.