Traffic prediction is important for Intelligent Transport System, and it is also the basis of many practical applications. However, traffic data are often highly non-linear and have complex spatio-temporal relationships, making this task challenging. In this paper, a new deep learning framework, Weighted Graph Convolutional Long Short-term Memory Network (WGCN-LSTM), is proposed for urban traffic flow prediction. The model combines the advantages of graph convolutional networks (GCN) and Long short-term memory networks (LSTM) to capture both spatial and temporal features in traffic flow data. WGCN-LSTM can reflect the actual network topology more accurately by weighting the road length and traffic flow. The experimental results show that WGCN-LSTM has higher prediction accuracy than other baseline models on two real traffic flow data sets, which verifies the effectiveness and applicability of this method in complex traffic prediction tasks.