In this paper, we first show DNS-over-HTTPS (DoH) tunneling detection methods verified to be effective over IPv4 can be applied to IPv6, and then propose a new model called CCSv6, using attention-based convolution neural network to build classifiers with flow-based features to detect DoH tunneling over IPv6, achieve 99.99% accuracy on the IPv6 dataset. In addition, we discuss the influence of various factors such as locations or DoH resolvers on the detection results in detail over IPv6. All the more important, our model shows better transfer learning ability, which can achieve the F1-score of 96% when trained on the IPv6 dataset and tested on the IPv4 dataset.