Eight previously undescribed diterpenoids, rosins A−H, and nine known diterpenoids were isolated from the resin from Pinus kesiya var. langbianensis (A.Chev.) Gaussen ex Bui (Pinaceae) extracted with 95% ethanol. Their structures were determined by nuclear magnetic resonance spectroscopy, mass spectrometry, J−based configuration analysis (JBCA), NOESY spectra, calculated NMR chemical shifts and electronic circular dichroic (ECD) spectra. All compounds were evaluated for their protective effects in LPS-treated human normal lung epithelial cells (BEAS-2B), and the cell viability was significantly increased after treatment with compounds 5, 10, 12, or 15 at a concentration of 10 μM.