This paper proposes a novel regularized adaptation method to improve the performance of multi-accent Mandarin speech recognition task. The acoustic model is based on long short term memory recurrent neural network trained with a connectionist temporal classification loss function (LSTM-RNN-CTC). In general, directly adjusting the network parameters with a small adaptation set may lead to over-fitting. In order to avoid this problem, a regularization term is added to the original training criterion. It forces the conditional probability distribution estimated from the adapted model to be close to the accent independent model. Meanwhile, only the accent-specific output layer needs to be fine-tuned using this adaptation method. Experiments are conducted on RASC863 and CASIA regional accented speech corpus. The results show that the proposed method obtains obvious improvement when compared with LSTM-RNN-CTC baseline model. It also outperforms other adaptation methods.