As the substrate material for IC fabrication, the uniformity of silicon single crystal and the size and density of micro defects are highly required. In the process of growing silicon single crystal by traditional Czochralski (Cz) method, the crystal diameter is controlled by the growth-rate, so the growth-rate is always in a fluctuating state. The effects of constant growth-rate on crystal uniformity and defect density and size were still rarely studied. In this research, a 300 mm diameter silicon crystal was grown at the rate of 35±0.7 mm/h. The resistivity distribution between wafers and within a wafer, and the distribution of FPD in the wafer were detected, the results show that the resistivity uniformity of the crystals was improved and the density of FPD are reduced at the lower growth-rate fluctuation stage.