The Printed Circuit Heat Exchanger (PCHE), distinguished by its outstanding performance, holds promise as a replacement for the conventional main heat exchanger in integrated reactors, ultimately boosting the compactness of pressure vessels. As a pivotal component within the energy conversion system of the I2S-LWR, the performance of the PCHE significantly influences both the reactor's safety and economy. This study focuses on the optimization of the PCHE in the I2S-LWR. A simplified numerical model of the PCHE was developed by utilizing the microchannel unit based on the CFD and validated through microchannel flow and heat transfer experiments. A multi-objective optimization analysis of the PCHE was conducted, with the cross-sectional aspect ratio, number and length of microchannel serving as decision variables, and the pressure drop and overall volume as the objective functions. Sensitivity analysis of the objective functions was performed using the Response Surface Method (RSM), and an optimization model for the PCHE was formulated and refined through the application of the Non-dominated Sorting Genetic Algorithm II (NSGAII). Multiple optimized design schemes were derived by using the TOPSIS method, and validated through the established CFD model. This study introduces a highly promising approach to forecasting and enhancing the attributes of PCHE.