Heavy metals such as zinc and copper can be entered into the agricultural soils in different ways especially by human activity. These elements are accumulated in the soil due to their low mobility over time. Accumulated elements in the soil are entered into the human food chain in various ways, causing health risks to humans and other animals. Therefore, assessing the process of heavy metals accumulation in the soil is essential to prevent soil pollution as well as environment protection and should be considered by researchers and program planners in different management levels. The purposes of this study are evaluation of zinc and copper mass balance by randomized modeling in agricultural soils of Kermanshah province based on county and province (district) scales, identification of dominant entering pathways of zinc and copper in the soil, determining the amount of dust deposition during the spring and summer and finally delineating the amount of combination of these elements in dust and its contribution to heavy metals entering into the agricultural lands. 214 samples including, surface soil (0-20 cm), plant (wheat, barley, chickpea, maize, beet, alfalfa and clover), dust, animal manure, chemical fertilizer and compost were collected from an area of 17118 square kilometers and then total and absorbable concentration (DTPA) of zinc and copper and soil properties including pH, salinity, cation exchange capacity, organic materials, lime and total manure phosphor were measured. MFA (Mass Flux Assessment) model was used to modeling the process of elements accumulation supported by randomized method based on mass balance and using a combination of Latin Hypercube method and Mont-Carlo stimulation in agronomic ecosystems of Kermanshah, Sangher, Gilangharb, Ghasreshirin, Sahneh, Sare-pole Zahab, Kangavar, Paveh and Javanroud counties. Thus, agronomic information such as crop type, cultivation area, yield, type and number of livestock, amount of used chemical fertilizers, compost and pesticides, amount of atmosphere deposition (as a new model input for closing model results to reality) and also the information about zinc and copper concentrations in plans, types of fertilizers and the dust were used. The results demonstrated that the average of measured concentrations of total zinc and copper in studied soils are lower than critical levels. The results indicate the accumulation of zinc and copper in agricultural lands of studied counties except for Kermanshah having negative accumulation rate. The highest accumulation rates of zinc (1172 g ha -1 yr -1 ) and copper (270 g ha -1 yr -1 ) were measured in Paveh while the lowest accumulation rates of zinc (-26g ha -1 yr -1 ) and copper (6 g ha -1 yr -1 ) were measured in Kermanshah. Although, the animal manure and atmosphere sitting down are the most important pathways for zinc and copper entering into the studied agricultural lands in county scale, compost (61-74 %), animal manure (23-33 %) and atmosphere sitting down (3-5 %) are the most important pathways in state scale. Model uncertainty analysis results revealed that, animal manures are the most important factor of uncertainty on the accumulation rate of zinc (79 %) and copper (61 %) in the studied area. Key Words Mass Balance Modeling, Zinc and Copper, Agronomic Ecosystem, Keranshah Province