We study the property of magnetopolaron in a parabolic quantum dot under the Rashba spin–orbit interaction (RSOI) by adopting an unitary transformation of Lee–Low–Pines type and the variational method of Pekar type with and without considering the temperature. The temporal spatial distribution of the probability density and the relationships of the oscillating period with the RSOI constant, confinement constant, electron–phonon coupling strength, phonon wave vector and temperature are discussed. The results show that the probability density of the magnetopolaron in the superposition of the ground and first excited state takes periodic oscillation (T
0/period) in the presence or absence of temperature. Because of the RSOI, the oscillating period is divided into different branches. Also, the results indicate that the oscillating period increases (decreases) when the RSOI constant, electron-phonon coupling strength and phonon wave vector (the confinement constant) increase in a proper temperature, and the temperature plays a significant role in determining the properties of the polaron.