The rural road network scale prediction is one of the main contents of "Four-merit rural roads" planning. In view of the limitations for a single forecasting method, this paper proposes a combined forecasting method based on the theory of entropy weight, which reasonably allocates weight of the land coefficient method, the density of population and economic method, and connectivity method. Taking the rural road in Anji county as an example, it fits the rural road network scale and verifies the validity and rationality of the three single forecasting methods. Through three kinds of error indexes of absolute average error, absolute average percentage error and root mean square error, it constructs evaluation matrix, and respectively calculates the weight coefficients of the three single forecasting methods，namely 0.115 4，0.240 3 and 0.644 3，which verify that entropy weight method can distribute weight coefficients objectively. It shows that the combination forecasting method can reduce the forecasting risk of a single model, which predicts the rural road network scale in future years.