The invention belongs to rocket boost conveying system, and particularly relates to a precision measuring method for flow resistance of real propellant flowing through a conveying pipe, which aims to precisely measure actual flow resistance value of the conveying pipe under given propellant flow rate. The measuring system includes a propellant storage tank, wherein three branches are externally connected to the storage tank; the two branches are storage tank outflow branches; the propellant is sequentially connected with a test piece of the conveying pipe through a gear pump, a flow rate, a ball valve and a stainless steel corrugated pipe; the third branch is a propellant back flow path and includes a ball valve; a differential pressure gage is arranged between two conveying pipe inlets; a differential pressure gage is arranged between any conveying pipe inlet and conveying pipe outlet; and two ends of the differential pressure gages are connected with a measuring terminal through a needle valve. The two groups of differential pressure gages are used for measuring differential pressure, and the gear pump achieves flowrate variable frequency adjustment. The precision measuring system and method can precisely measure the actual flow resistance value of the conveying pipe, so as to check the design reasonableness of the conveying pipe.