在一無碰撞且磁化的電漿中，壓力或溫度會呈現非均向性，而導致不穩性的產生；尤其是，當電漿的壓力滿足P//>P⊥+B02/μ0條件時，會產生救火管不穩定性。過去的研究顯示，救火管不穩定性之發展包含兩個階段：第一是線性階段，此時的磁場擾動會快速地成長，而非均向性也會被減少至接近救火管不穩定性的發生門檻；第二階段的發展速度趨緩，在這個階段中磁場擾動和非均向性都緩慢地減小。在本研究中，我們發展一混合粒子碼，模擬救火管不穩定性，以期探討與分析電漿如何由線性階段發展至非線性階段的機制。我們發現，在線性階段中，磁力線和粒子與其所產生之電流互相交互作用而成長，而到了飽和階段時，粒子由於複雜的迴旋運動而變得混亂，此時磁力線和電流的關係不再顯而易見。 In a magnetized, collisionless plasma, the pressure or temperature is often anisotropic. The pressure anisotropy may lead to the instability; in particular, if the plasma satisfies the condition of P//>P⊥+B02/μ0, the fire-hose instability may occur. Past studies have shown that the evolution of fire-hose instability consists of two stages: the linear stage where the magnetic field fluctuation grows rapidly and the plasma is brought back to the marginal stability, and the second stage where the evolution becomes slower and the magnetic field fluctuation is reduced. The mechanism that drives the plasma back to the marginal instability however is still unclear. In this study we develop a hybrid particle code to simulate and analyze the detailed evolution of the fire-hose instability. It is found that the magnetic field fluctuations and the ion motions and the associated current flows are highly interacting with each other at the linear stage. At the saturation time the particle motions become chaotic because of the complicated gyro-motions and the magnetic field fluctuation gradually reduces; after that the coupling between the magnetic field and particle motions become less obvious.