Line-start permanent magnet synchronous motors (LSPMSMs) are energy-efficient motors that can be an alternative to asynchronous motors in applications with direct powering from a three-phase network. However, LSPMSMs have difficulties with synchronization during start-up, the success of which depends on the torque and the moment of inertia of the loading mechanism. For this reason, it is advisable to investigate the process of LSPMSM launching by means of mathematical modeling using an ordinary differential equation model with lumped parameters. The parameters of this model can be obtained by identifying them in transient processes. This paper presents a novel identification method based on experimentally obtained data on instantaneous active and reactive powers during the LSPMSM start-up at no-load. Using the proposed method, parameters of a commercially available 0.55 kW, 1500 rpm LSPMSM were identified. A comparison of experimental and simulation waveforms calculated using the obtained parameters is presented. © 2023 IEEE.