Abstract: The Hongte depression located in the Erlian Basin is a Mesozoic and Cenozoic fault basin developed on the Hercynian folded basement. The diagenetic history and diagenetic sequences are examined on the basis of thin sections, X-ray diffraction, SEM and cathodoluminescence analysis for the samples from more than twenty wells in the depression. The diagenesis in the depression comprises compaction, cementation, solution, alteration, replacement, transformation and recrystallization of clay minerals, filling of hydrocarbons and tectonic stress of the Lower Cretaceous strata including the clastic reservoirs K₁bt¹ and K1^ba.