This study aim to investigate the effect of different slops on mechanical lumbosacral angles and lumbar stability of healthy and mechanical low back pain (LBP) persons. This case- control study was performed on 38 females (18 LBP and 20 healthy subjects) who were referred to the Hospital in sari. At the beginning, Subjects’demographic data were recorded. In order to measure lumbosacral angles and  lumbar spine stability evaluation, three lateral radiography plots in state of standing on various slope (­ο, +3.7, -3.7) were prepared. There were no significant differences between the biomechanical lumbosacral angles by standing on the various slopes, within and between 2 groups (LBP and healthy females) (p≥0.05).There was more lumbar instability in females with LBP and lumbar mechanical stability was significantly difference between 2 groups in each slope (P +=0.023, P –=0.009, P 0=0.004). Although, lumbar stability was not significantly different within each LBP and healthy groups, on the various slopes (p≥0.05). It seems that lumbar instability may increases in mechanical LBP, that won’t manage by various levels of slop.