Accurate lithologic evaluation of tight reservoirs and fine oil- source correlation are the important basis for “seven characteristics” evaluation and exploration and development of tight oil and shale oil. Taking the QP1 well in the northern part of the Songliao Basin as an example, this study employed the method of precise and accurate description of lithology with “three scales” of centimeter, millimeter and micron, to analyze accurate description and evaluation of dense reservoirs. The results indicate that the lithologic strips in the same section increase from 11 conventional ones to 14 precise description by centimeter level and 135 by millimeter level. The outer front facies of delta in different sedimentary facies with various ratios of total sandstone thickness to formation thickness increases from the conventionally described 17. 16% to the accurately described 29. 87%, the inner front facies of delta increases from 45. 29% to 47. 55%, and the shore- shallow lake facies increases from 6. 53% to 9. 93%. The lithology and reservoir properties of compact reservoirs with different continental sedimentary facies were quantitatively evaluated. Based on the accurate description and evaluation of tight lithology, precise sampling and hydrocarbon analysis techniques for millimeter- scale rock samples are established. Fine oil- source correlation and oil- bearing evaluation of tight reservoirs and millimeter- scale samples show that the same mudstone section and centimeter- millimeter thin sand strips are identical in hydrocarbon characteristics, the thin sand strips and their contact mudstones can constitute a source- reservoir- cap assemblage；the hydrocarbon characteristics of different mudstone sections are obviously different, and the type and maturity of the source material are similar；the hydrocarbon characteristics of reservoirs in different sandstone sections are obviously different, but similar to the underlying mudstone formations, and vertical mudstone thickness of 2. 9 m and sandstone thickness of 1. 1 m can form source- reservoir- cap assemblage, which has the source- reservoir allocation relationship of near- source accumulation of “lower generation and upper storage”. It is pointed out in this study that the inner front facies of the delta is dense oil and the outer front facies is dense oil and shale oil. Therefore, shore- shallow lake facies is the deployment direction of favorable areas for shale oil exploration.