Jute and cotton fibres are most important natural fibres. Cotton is being blended with jute fibre to impart comforts, technical properties, flexibility for producing diversified products and cost reduction. As cotton and jute both are natural cellulosic fibres, determination of individual percentage ratios in their blending by chemical analysis is difficult. Presence of individual fibres have been identified by FTIR analysis as jute possesses aromatic ring group and cotton does not. Fibre fineness analysis is also helpful to ensure the existence of jute fibre in jute-cotton blended materials. Here, blending ratio of jute and cotton fibre has been determined by dyeing and weighing process. Physical identification of component fibres by absorbing a selective dye with respect to jute has been helpful to differentiate and separate the jute-cotton fibres. In this respect, basic dye is substantive to jute fibre and pure cotton fibre has very poor substantivity to that dye. Using this technique, Jute and cotton fibres have been identified and manually separated from their blended roving and yarn. Their percentage ratios have been determined by weighing the separated fibres. This experimental results reveals that the Jute/Cotton weight percentage of jute cotton blended yarn was found as 16.58/83.42 respectively whereas the initial feed ratio of these fibres in blow room was 30/70. This research will help the spinners of jute-cotton blended yarns to control their desired product requirements and quality.