Speech enhancement generative adversarial network (SEGAN) is an end-to-end deep learning architecture, which only uses the clean speech as the training targets. However, when the signal-to-noise ratio (SNR) is very low, predicting clean speech signals could be very difficult as the speech is dominated by the noise. In order to address this problem, in this paper, we propose a gated convolutional neural network (CNN) SEGAN (GSEGAN) with noise prior knowledge learning to address this problem. The proposed model not only estimates the clean speech, but also learns the noise prior knowledge to assist the speech enhancement. In addition, gated CNN has an excellent potential for capturing long-term temporal dependencies than regular CNN. Motivated by this, we use a gated CNN architecture to acquire more detailed information at waveform level instead of regular CNN. We evaluate the proposed method GSEGAN on Voice Bank corpus. Experimental results show that the proposed method GSEGAN outperforms the SEGAN baseline, with a relative improvement of 0.7%, 28.2% and 43.9% for perceptual evaluation of speech quality (PESQ), overall Signal-to-Noise Ratio (SNRovl) and Segmental Signal-to-Noise Ratio (SNRseg), respectively.