arrive是不及物动词,后面加宾语时要加上适当的介词,at /in
一般来说,大地点用in 小地点用at
I arrived in Beijing at six o'colock.
I arrived at the school gate at six o'colock.
而reach是及物动词,及物动词的特点是,用面一要在加宾语,宾语一定不能省略,而且不用任何介词.
表示到达某地还有get to .
I got to the the school gate at six o'colock.
但是上面get to /arrive,如果后面的宾语是副词的话,都不能加介词
I got home/arrived home/reached home.