BIOCHLOR is an easy-to-use screening model that simulates remediation by natural attenuation (RNA) of dissolved solvents at chlorinated solvent release sites. Programmed in Microsoft Excel spreadsheet environment and based on Domenico analytical solute transport model, the software is widely applied to simulate 1-D advection, 3-D dispersion, linear adsorption, and biotransformation via reductive dechlorination. This model includes seven parameter modules: advection data, dispersion data, adsorption data, biotransformation data, general data, source data, and field data for comparison. The values of advection data, dispersion data, adsorption data, and biotransformation data are respectively changed while the others are kept constant to compare the simulated values. Variation diagrams of the simulated value are drawn to analyze the levels of model response to each parameter. The purpose of sensitive analysis is to test the level of the influence of parameters, and to analyze the annoyance level of error. If the parameter sensitivity in a certain model is not high, allowable error threshold can be bigger; on the contrary, the minor differences of parameters can lead to disparity in the results and decrease of simulation forecast precision. More efforts and funds should be invested for the highly-accurate parameters.