Abstract: Considering the timevalue of the funds is ignored in the traditional calculation of economic diameter for pulp conveying pipe and the process to get the local pressure head loss through the chart by estimating the diameter brings inconvenience and deviation, the capital timevalue is taken into consideration and the process to get the equivalent length of piping accessories is simplified in this paper, furthermore, the formula for economic diameter is obtained and an example is provided at the same time. The results showed that the economic diameter with considering the capital timevalue is about 103 %-126 % smaller than that with traditional method when pulp consistency ranges from 1 % to 35 %, accompanied by the pipeline construction costs drop 165 %-201 % and the overall economic efficiency saves 2631-2907 yuan per meter, so that the project construction costs and later pipeline renewal expenses are effectively reduced.