This paper presents a new method to estimate online four parameters of the interior permanent magnet synchronous motors (IPMSM), including stator resistance, d- axis inductance, q-axis inductance and permanent magnet flux linkage. The proposed method is based on the neural network with the training data taken from experiments, which were preprocessed before feeding to the input of the neural network model. The proposed online parameters estimation method is evaluated by comparing the estimation accuracy and the updating time with other conventional online methods, such as Extended Kalman Filter, Recursive Least Square and the Adaline Neural Network. Extensive numerical simulations have been conducted to verify the effectiveness and the accuracy of the proposed method.