In order to properly calculate the Friction field fracturing string, with the method of Reynolds number is similar ,To obtain a relation about string friction coefficient of indoor and outdoor ,and a relation about friction、displacement or length. By measuring the slick water of indoor string friction, calculate the fracturing string resistance of outdoor string friction. Adopt the relation in combination with field test validation,By comparing the CalculationSString friction resistance,The relative error of calculated result less than 7%,This method can be approve a calculation model for large slick water shale gas fracturing friction prediction.