Abstract：A lattice passive solar heating wall (LPSHW) can remarkably improve the heating performance of passive solar heated buildings. Many parameters affect the thermal performance of the LPSHW so that it is not realistic to scrutinize the thermal performance of the LPSHW experimentally. This paper develops a three-dimensional transient heat transfer model of the LPSHW, based on which a computer simulation program is developed in FORTRAN language. The model predictions agree quite well with experimental data. The program can be used to simulate and evaluate the transient thermal performance, to analyze the sensitivity and the effect of climate, and to optimize LPSHW structural parameters. Hour-by-hour computer simulations are run with the program to analyze the sensitivity of a variety of parameters of the LPSHW. The calculations are rerun many times with structural parameters changed one at a time so that the effect of the changed structural parameter on the thermal performance of the LPSHW can be assessed. From the sensitivity analysis, the optimum configuration is thus obtained. The comparison between the LPSHW and the Trombe wall is made thereafter. Under the chosen conditions, thermal efficiency is 30.2% for the LPSHW and 22.6% for the Trombe wall.