Abstract: The background and the method for the power uprating in nuclear power plants (NPP) in China were described, and the specifications on NPP power uprating in related laws and standards were analyzed and summarized. The classification of NPP power uprating was overviewed, and the specific requirements and main methods for NPP small range uprating were analyzed. Based on the analysis of NPP power and the calculation method for the uncertainty, the main parameters having effects on the calculation error for the thermal power of the core were specified, which were the main feedwater flow and the main feedwater temperature. The methods to apply the optimization of parameter uncertainty in the power uprating was analyzed and summarized, which was to add new differential pressure transmitter or ultrasonic flowmeter and  temperature transmitter to optimize the parameter uncertainty. The economy for NPP small range power uprating was summarized.