The public’s demand for more and better forest landscapes is increasing as scenic forest tours flourish in China, especially in the capital, Beijing. How to improve the quality of scenic forests has become one of the greatest concerns of urban foresters. Although numerous studies have focused on scenic forest management, to date, no reports have been found on developing a quality assessment index system for scenic forest assessment. In this study, a simple and scientific index system was established using an analytical hierarchy process (AHP) to quantitatively assess scenic forest quality. The index system is composed of four scales: individual tree landscape quality, in-forest landscape quality, near-view forest landscape quality and far-view landscape quality. The in-forest landscape quality was determined by horizontal and vertical stand structures, species composition and under-canopy landscape traits. Near-view forest landscape quality was mainly determined by patch characteristics, seasonal change, visibility, color change of patches and stand age class. To test the validity of our quality assessment index system, scenic forests in Xishan were used as a case study. The results show that near-view forest landscape was the most important scale for the overall quality of the scenic forest, according to the priorities of the criterion layer, and the second most important scale was far-view forest landscape. Seasonal change, patch color contrast, patch distribution and patch shape accounted for 52.2% of the total of 13 indices in the near-view forest landscape. The integrated quality of scenic forests in Xishan was at an average level, and the in-forest landscape, near-view landscape and far-view landscape had below average quality.