Though the lengthened shrink-fit holder (LSFH) is widely applied in high speed milling of the parts characterized by deep cavities at present,its design and selection mainly depends on the experience and lacks a correct theoretical guidance.In this paper,attention is focus on the radial grip rigidity of the matching of LSFH and cutter in high speed milling.Based on the experiment modal analysis (EMA) technique,an accurate finite element model of the matching of LSFH and cutter is established firstly.Subsequently,the influence of different interference,grip length and spindle speed on the grip rigidity of LSFH are analyzed.The analysis results show that there is a reasonable interference and grip length between the LSFH and cutter so that to have a steepless grip and have a good radial grip rigidity and at the same time to avoid the strength of LSFH to exceed it’s yield limit which will reduce the precision and service life of LSFH,besides when spindle speed reach a extension the weakening influence of the centrifugal force on the radial grip rigidity of the matching of LSFH and cutter should been taken into account.Finally,the finite element analysis results are verified based on the construction ofmeasurement method of the grip rigidity and the results fit very well.The studies provide a theoretical basis for the design,selection and the serialization and standardization of the matching of LSFH and cutter.