Although there exists quantities of GPS data of floating car, partial links lack real data during some certain period of time. Therefore, we can't estimate target link travel time. Considering the problem of sparse data when using floating car data estimating link travel time, we put forward a kind of inferred method based on big data of floating car. We designed a three-layer artificial neural network model, whose input information and output information are the feature relationship and the travel time ratio between target link and adjacent link respectively. We obtained traffic spatiotemporal association relationship using historical big data of floating car and then inferred link travel time. The model was verified by historical big data of Wuhan's floating car from March to July, 2014 and the MAPE of estimated value of link travel time is less than 25% which proved the effectiveness of the proposed method.