Protocol development for predicting dispersion coefficient caused by velocity gradient using mobile bed model tank on the straight channel has been investigated by Adhi . This study develops a protocol, which uses mathematical modeling tool Resources Modeling Associates (RMA) as a continuation from Adhi’s physical modeling. Objectives of the study are (1) record the numerical modeling process to determine dye tracer dispersion coefficient in a straight channel using RMA program, and (2) develop experiment protocol in simulating a two-dimension flow to determine dye tracer dispersion coefficient in a straight channel. The RMA program is used to compare the dispersion visualization of dye tracer between numerical modeling and experimental modeling. The dispersion coefficient observed earlier by Adhi is used as the input for the model. Using the integrated RMA program, this protocol complementing process generally consists of four main components: straight channel’s geometry preparation using RMA-GEN, hydrodynamic flow simulation using RMA-10, constituent dispersion simulation using RMA-11, and data interpretation. The conservative solution’s dispersion coefficient values are analyzed using the Sum of Squared Errors (SSE). The least SSE value is 3354 for dispersion coefficient in x-direction 610 cm2/s and dispersion coefficient in y-direction 80 cm2/s. The result of the study is a protocol to determine dispersion coefficient of the conservative solution in mobile bed model tank experiment using RMA program.