float angle = 40;
        Vector3 v = rotatePoint.transform.position;
        Debug.Log("旋转向量 " + v + "__自身 " + cube.transform.rotation);
        v.Normalize();
        Debug.Log(v);

        float f = angle * Mathf.Deg2Rad / 2;
        float sinHalfAngle = Mathf.Sin(f);
        float cosHalfAngle = Mathf.Cos(f);
        Quaternion q = new Quaternion(sinHalfAngle * v.x, sinHalfAngle * v.y, sinHalfAngle * v.z, cosHalfAngle);
        Debug.Log("旋转的 ;" + q + "__" + q.eulerAngles);

        Quaternion vv = cube.transform.rotation * q;
        Debug.Log("预估欧拉1 ：" + vv + vv.eulerAngles);

        cube.transform.Rotate(v, angle);
        Debug.Log("实际欧拉2 ：" + cube.transform.rotation + "__" + cube.transform.rotation.eulerAngles);

        Debug.Log(rotatePoint.transform.position);

 参考网址：

Unity--四元数（Quaternion）和旋转_阿成_的博客-CSDN博客

Unity-四元数_unity 四元数相乘_我和BUG只能活一个的博客-CSDN博客