The water blocking law of the shrub vegetation distribution area in a river was ascertained by examining the characteristics and quantitative characteristics of flow resistance generated by shrub vegetation trunks and branches. Here, we present a prototype vegetation volume correction coefficient and a method for determining shrub vegetation hydraulic radius. The calculation formula of the shrub vegetation resistance coefficient is theoretically derived, and the relationship between the vegetation resistance coefficient and the vegetation Reynolds number with the characteristic length of the vegetation hydraulic radius is established in combination with a flume experiment. Our results indicate that:introduction of a prototype vegetation volume correction coefficient and a shrub vegetation hydraulic radius results in a more accurate shrub vegetation resistance calculation. The relationship between vegetation resistance coefficient and vegetation Reynolds number is an exponential function, and it decreases monotonically with an increase in the vegetation Reynolds number. Results from our flume experiment are in strong agreement with these findings.