Carbon Nanotube (CNT) is a material consisting of carbon atoms arranged in a series of condensed benzene rings that are coiled into a tubular structure. CNTs are used in various fields, such as reinforcing materials, coatings and films, biotechnology and biomedicine, and nano electromechanic systems (NEMS). The application of CNT in the biotechnology and biomedical fields as a nanopipe for carrying fluids is due to its high elastic modulus, good thermal and electrical conductivity, and other superior mechanical properties. One of the phenomena that can reduce CNT performance is flutter, so fluid-structure interaction is one of the important considerations in the design and application of CNTs. This study analyzes the effect of mass ratio on flutter instability due to flow in the CNT cantilever using the finite element method. Meanwhile, the system's responses are calculated using the Newmark method time scheme. The structural characteristics of the CNT were modeled as the Euler-Bernoulli beam. In this case, the fluid flowing in it is characterized in terms of two parameters, namely the average flow velocity (U) and the fluid mass density (per unit length). The results showed that the analysis of the response in the time domain is very sensitive to changes in flow velocity, the critical speed will decrease with an increase in the aspect ratio. and the mass ratio affects the flutter stability limit, where the larger the mass ratio for a given fluid density, the higher the flutter stability limit. The findings also revealed that the higher the density of the fluid flowing through the CNT, the lower its ultimate stability limit.