The construction of No.I line of Tianjin Subway will improve the current situation of city's traffic to a great extent, it exists an important meaning to promote the construction of Tianjun City and to push its ec onomic development forward. This engineering work will produce somewhat influenc es on city's ecologic environment during construction and operation periods. The positive and passive influences of the subway engineering works on the city's e cologic environment are analyzed in detail concerned with the following aspects, such as the noise, vibration, dush raising and soil erosion during the construc tion period, and pushing the economic development forward, relaxing traffic on g round level, improving environmental quality during the operation period, etc.