直接上代码:

    private Animator anim;
    private AnimatorController animController;

    private void Awake()
    {
        anim = GetComponent<Animator>();
        animController = anim.runtimeAnimatorController as AnimatorController;
        if (animController)
        {
            //传入layerIndex  要更改速度的状态名称和speed
            SetAnimatorSpeed(0, "TestState", 2f);
        }
    }

    /// <summary>
    /// 在运行时更改Speed 运行结束时不会恢复到之前的Speed 对文件进行了更改  
    /// 如果要恢复 在需要的时机再调用一次方法
    /// </summary>
    private void SetAnimatorSpeed(int _layer, string _stateName, float _speed)
    {
        for (int i = 0; i < animController.layers[_layer].stateMachine.states.Length; i++)
        {
            if (animController.layers[_layer].stateMachine.states[i].state.name == _stateName)
            {
                animController.layers[_layer].stateMachine.states[i].state.speed = _speed;
            }
        }
    }

    private void OnDestroy()
    {
        SetAnimatorSpeed(0, "TestState", 1f);
    }