Considering Rashba spin orbit interaction and spin quantum transport in the spin field effect transistor, we study the influence of the barrier strength on the spin coherence transport in spin field effect transistors. It is found that when the barrier strength is weak, the tunneling junction conductance exhibits oscillatory phenomenon obviously with increasing Rashba spin orbit interaction strength. The conductance exhibites barrier-dependent conductive switching effect as the barrier strength increases. When the barrier strength gradually increases, parallel conductance exhibits a monotonicall decreasing trend, while the anti-parallel conductance fluctuates, and such a fluctuation leading to the tunneling magnetoresistance also exhibits oscillatory phenomenon with the variation of barrier strength . For a suitable thickness of quasi one-dimensional electron gas, the tunneling magnetoresistance value can produce positive and negative inversion, and the effect will shed light on the application of spin information storage electronic device.