The tidal river network area has the characteristics of criss-crossed water systems and developed cities. High intensity land use and development leads to serious hydrological pollution and degradation of ecological environment functions of urban landscape lakes. Taking the typical urban landscape lake in the river network area - Baiyun Lake in Guangzhou as the research object, this paper constructed a two-dimensional hydrodynamic and water quality coupling model to study its eco-environmental water demand and its water supplement schemes. The results show that the two-dimensional hydrodynamic and water quality coupling model in the river network area based on Mike21 can effectively simulate the temporal and spatial evolution law of water quality in urban landscape lakes, and the relative errors between the simulated values and the measured values are less than 0.20, Nash efficiency coefficients are greater than 0.75. By jointly using Baiyun Lake sluice and pump hydraulic engineering to dispatch and replenish water, the assurance rates of eco-environmental water demand of Baiyun Lake and its connected rivers are basically 100%, the contents of TN and TP meet the fourth class water quality. The research results can provide reference for ecological and environmental governance of urban landscape lake of polluted river network.