The 20# dam section in Wuxikou water conservancy project is roller-compacted concrete gravity dam, analysis of the strainmeter data shows that some of the strainmeters’ values abnormally increased, so it’s speculated that the strainmeters were buried in the tensile stress area of the dam section, and that the crack showed up near the sixth strainmeter. In the meantime, it’s considered that stress and strain will grow to be steady. It’s suggested to undertake intensive observation near sixth strainmeter and pay attention to data compilation so as to know the development of cracks. Temperature control measures should be taken among other section of the dam to prevent cracks in mass concrete.