Abstract: This paper mainly studies the spin-up control of spinning linear electrodynamic tether formation (SLETF) consisting of three nano-satellites connected by two conductive tethers. SLETF is promising in constructing observation platforms, artificial gravity, space station, and so on, but the system is unstable during spin-up process as coupled tethers may become slack or even entangled with tethered satellites due to significant tether deformation. To deal with this unresolved problem, this paper mainly studies the spin-up control of a SLETF by considering tether flexibility. First, two models are used: The Lagrangian model is used for controller design and the flexible lumped model is used for analyzing flexible tether motions, Then, uncontrolled tether deformations are examined under the open-loop on/off program, Third, to stabilize tether deforamation and ensure tracking spinning rate at the same time, an optimal controller based on Bellman dynamic programming is proposed for the spin-up process. Numerical results show that, under the regulation of the proposed optimal controller, tether deformations are reduced to an insignificant level (95.2% of linear tether length), and tethers spin synchronically around the designated spinning rate.