Abstract: Quantum Neural Networks (QNN) is a promising area which integrates Arti-ficial Neural Netowrk(ANN) with quantum computing. The field of QNN is discussed, in particular, the motivation of ANN towards QNN, the advantages and the possible candi-dates for the implementation of QNN. Several QNN models are introduced in details and their architecture, learning algorithms and some properties are explored. The applications to pattern recognition, computing entanglement and multivariable functions approximation are analyzed.