The Guanghua Formation in Longjiang Basin deposited continuously and is exposed in integrity, with abundant fossils of Jehol Biota, making it one of the key sections to probe the origin, evolution and radiation of the Jehol Biota in the middle of Da Hinggan Mountains. This study carried out a precise measurement for the section of Guanghua Formation. It is believed that the Guanghua Formation conformably overlies andesitic welded tuff of the Longjiang Formation, with part covered unconformably by basalt of the Ganhe Formation. Three lithological units have been recognized from bottom to top. Systematic sampling and identification for corresponding biota fossils were carried out, and this has greatly enriched the biota category of Jehol Biota in the middle of Da Hinggan Mountains. Based on newly collected fossils and previously published data, authors established the assemblages of various fossils in the middle of Da Hinggan Mountains, which include limbs, ostracods, plant fossils, insects and others, and further discussed their characteristics. The LAICPMS UPb zircon chronology study of the lower to middle sections of Guanghua Formation reveals that the Jehol Biota in the Longjiang Basin occurred at time of 1254±14Ma to 1201±11Ma, with an span of roughly about 500 million years, reflecting that the Jehol Biota throve from early to middle Apter period. According to paleontological characteristics and our previous studies, it can be concluded that the paleoenvironment of the Jehol Biota in the Longjiang Basin may be the intermittent or seasonal lakes, and the paleoclimate should be in the warm and humid seasonallychanging warm zone, accompanied by the short term arid climate.