Abstract: According to the analysis of the factors that have effect on the accuracy of the core location, the effect of various parameters on the core positioning were quantization. In order to reduce the positioning error of the single point positioning method and the improved four-point centering average step length positioning method, a gauge precise positioning method is proposed, and successfully applied in a nuclear power plant. Results show that, this core positioning technology greatly reduces the measurement error during the core step length selection, and improves the coordinate point in the core minimum quantity from the traditional 7mm to 11 mm.