The spatial-temporal substitution method was applied to explore the effects of planting period on the soil fertility by soil nutrients and soil enzyme activities in cherry orchards around Tianshui region.It indicated that the quadratic function fitting could be used in analog the variations of soil nutrients and its enzyme (except polyphenoloxidase)activities with the increase of the planting period.Both soil nutrients and soil enzyme activities varied significantly with different periods of planting.A significant,even extremely significant correlation existed between planting years and soil organic matter,available phosphorus,sucrase activities, alkaline phosphatase activities,cellulase activities.So did with the correlations between soil enzyme activities and soil nutrients content.