GRO J1008-57, as a Be/X-ray transient pulsar, is considered to have the highest magnetic field in known neutron star X-ray binary systems. Observational data of the X-ray outbursts in GRO J1008-57 from 2017 to 2020 were collected by the Insight-HXMT satellite. In this work, the spin period of the neutron star in GRO J1008-57 was determined to be about 93.28 seconds in August 2017, 93.22 seconds in February 2018, 93.25 seconds in June 2019 and 93.14 seconds in June 2020. GRO J1008-57 evolved in the spin-up process with a mean rate of $-(2.10\pm 0.05)\times$10⁻⁴ s/d from 2009 – 2018, and turned into a spin down process with a rate of $(6.7\pm 0.6)\times$10⁻⁵ s/d from Feb 2018 to June 2019. During the type II outburst of 2020, GRO J1008-57 had the spin-up torque again. During the torque reversals, the pulse profiles and continuum X-ray spectra did not change significantly, and the cyclotron resonant scattering feature around 80 keV was only detected during the outbursts in 2017 and 2020. Based on the observed mean spin-up rate, we estimated the inner accretion disk radius in GRO J1008-57 (about 1 - 2 times of the Alfvén radius) by comparing different accretion torque models of magnetic neutron stars. During the spin-down process, the magnetic torque should dominate over the matter accreting inflow torque, and we constrained the surface dipole magnetic field $B\ge 6\times {10}^{12}$ G for the neutron star in GRO J1008-57, which is consistent with the magnetic field strength obtained by cyclotron line centroid energy.

GRO J1008-57作为Be / X射线瞬态脉冲星，在已知的中子星X射线双星系统中被认为具有最高的磁场。Insight-HXMT卫星收集了2017年至2020年GRO J1008-57中X射线爆发的观测数据。在这项工作中，GRO J1008-57中子星的自旋周期确定为大约2017年8月的93.28秒，2018年2月的93.22秒，2019年6月的93.25秒和2020年6月的93.14秒。GRO J1008-57演化了在分拆过程中的平均比率为$-（2.10\pm 0.05）\times$10 ^-4 S / d从2009年至2018年，并变成一个降速处理与速率$（6.7\pm 0.6）\times$从2018年2月至2019年6月为10 ^-5 s / d。在2020年II型爆发期间，GRO J1008-57再次具有旋转扭矩。在扭矩反转期间，脉冲轮廓和连续X射线光谱没有明显变化，并且仅在2017年和2020年爆发期间才检测到80 keV附近的回旋共振散射特征。基于观察到的平均自旋速率，我们通过比较磁中子星的不同吸积扭矩模型，估算了GRO J1008-57的内吸积盘半径（约为Alfvén半径的1-2倍）。在降速过程中，磁转矩应胜过增加吸入转矩的物质，因此我们限制了表面偶极子磁场$乙\ge 6\times {10}^{12}$ G代表GRO J1008-57中的中子星，它与回旋加速器质心能量获得的磁场强度一致。