Quantitative assessment of pain is vital progressin treatment choosing and distress relief for patients. However,previous approaches based on self-report fail to provide objec-tive and accurate assessments. For impartial pain classificationbased on physiological signals, a number of methods have beenintroduced using elaborately designed handcrafted features. Inthis study, we enriched the methods of physiological-signal-based pain classification by introducing deep Recurrent NeuralNetwork (RNN) based hybrid classifiers which combines auto-extracted features with human-experience enabled handcraftedfeatures. A bidirectional Long Short-Term Memory network(biLSTM) was applied on time series of pre-processed signalsto automatically learn temporal dynamic characteristics fromthem. The handcrafted features were extracted to fuse withRNN-generated features. Finely selected features from biLSTMlayer output and handcrafted features trained an ArtificialNeural Network (ANN) to classify the pain intensity. The hand-crafted features enhance the RNN classification performanceby complementing RNN-generated features. With our accuracyreaching 83.3%, comparison results on an open dataset withother methods show that the proposed algorithm outperformsall of the previous researches with higher classification accuracy.Therefore, this research is a good demonstration of introducinghybrid features for pain assessment.