The reserves of the geological model in the offshore fluvial reservoirs are influenced by the uncertain parameters, such as the structure, plane variogram, correlation between reservoir properties and seismic attributes, irreducible water saturation, lower limiting value of effective reservoir, volume coefficient, and oil-water interface. The root that causes these uncertain parameters is analyzed. Meanwhile, taking oilfield-Q in Bohai bay as an example, and by the integrated application of the Monte-Carlo method and stochastic modeling, the effects of the uncertainty parameters on the reserves are estimated quantitatively. The probability cumulative distribution curves of reserves and 3 probability reserve value which are the pessimistic reserves（P90）, expected reserves（P50） and optimistic reserves（P10） are obtained to predict the risk and potential of the reserves.