动名词、过去分词和不定式做主语时的区别？

不定式和动名词作主语的区别（过去分词不能做主语）
(1)动名词作主语通常表示抽象动作；而不定式作主语表示具体动作。
Smoking
is
prohibited(禁止)here．这里禁止抽烟。(抽象)
It
is
not
very
good
for
you
to
smoke
so
much．你抽这么多烟对你身体很不好。(具体)
(2)动名词作主语时，通常用以表示一件已知的事或经验。
不定式短语通常用来表示一件未完成的事或目的。
Climbing
mountains
is
interesting．爬山很有趣。(经验)
Driving
a
car
during
the
rush
hour
is
tiring．在高峰时刻开车令人厌烦。(经验)
(3）不定式做主语，一般用it当形式主语，把作主语的不定式短语后置。
It
took
me
only
five
minutes
to
finish
the
job.

先讲下动名词和现在分词的区别，动名词可充当主语，宾语，表语，介词宾语，定语等。但动名词和现在分词作定语是不同的，所以你问的应该是现在分词而不是动名词。
试举例：
a
swimming
boy这是现在分词
相当于
a
boy
who
is
swimming
a
swimming
pool这是动名词
相当于
a
pool
for
swimming
不定式，现在分词，过去分词作定语区别，从时态意义上试举例说明：
the
meeting
to
be
held
tomorrow
is
very
important.
将来
the
meeting
being
held
is
very
important.
现在进行
the
meeting
held
yesterday
was
very
important.
过去
从主动被动角度举例说明：
the
boy
playing
with
the
girl
is
tall.相当于the
boy
who
is
playing
with
the
girl,
现在分词作定语表主动
most
of
the
artists
invited
to
the
party
were
from
china.相当于most
of
the
artists
who
were
invited
to
the
party,
过去分词作定语表被动。