  This paper describes the PASH participation in TREC 2021 Deep Learning Track.
In the recall stage, we adopt a scheme combining sparse and dense retrieval
method. In the multi-stage ranking phase, point-wise and pair-wise ranking
strategies are used one after another based on model continual pre-trained on
general knowledge and document-level data. Compared to TREC 2020 Deep Learning
Track, we have additionally introduced the generative model T5 to further
enhance the performance.
