英语中什么时候加ing，什么时候不加?

be动词(is.am.are).介词后面加ing形式。还有固定的词组搭配要记住
某些动词后出现非限定性动词时只能用动名词作宾语，不能用不定式。常见的此类动词有：advise,
allow,
permit,
avoid,
consider,
enjoy,
finish,
give
up,
cannot
help,
imagine,
include,
keep,
keep
on,
mind,
miss,
put
off,
delay,
practise,
resist,
suggest,
depend
on,
think
about,
set
about,
succeed
in,
worry
about,
burst
out,
insist
on,
can’t
stand,
be
used
to,
get
used
to,
devote…to…,
look
forward
to,
pay
attention
to,
get
down
to等。如：
They
went
on
walking
and
never
stopped
talking.
他们继续走，说个不停。
I
found
it
pleasant
walking
along
the
seashore.
在海滩上走真是乐事。
（2）作介词的宾语
We
are
thinking
of
making
a
new
plan
for
the
next
term.
我们正考虑为下学期制定新的计划。
Shall
we
have
a
rest
or
get
down
to
doing
our
work?
我们休息呢还是开始干活？
（3）作形容词的宾语
The
music
is
well
worth
listening
to
more
than
once.
这种曲子很值得多听几遍。
We
are
busy
preparing
for
the
coming
sports
meet.
我们正为马上到来的运动会忙着做准备。
3、作表语
动名词作表语时句子主语常是表示无生命的事物的名词或what引导的名词性从句。表语动名词与主语通常是对等的关系，表示主语的内容，主语、表语可互换位置。
Your
task
is
cleaning
the
windows.
你的任务就是擦窗户。(Cleaning
the
windows
is
your
task.)
What
I
hate
most
is
being
laughed
at.
我最痛恨的就是被别人嘲笑。
(Being
laughed
at
is
what
I
hate
most.)
4、作定语
动名词作定语往往表示被修饰词的某种用途。如：
a
walking
stick
＝a
stick
for
walking=a
stick
which
is
used
for
walking
a
washing
machine=a
machine
for
washing=a
machine
which
is
used
for
washing
a
reading
room=a
room
for
reading=a
room
which
is
used
for
reading
a
measuring
tape=a
tape
for
measuring=a
tape
which
is
used
for
measuring
sleeping
pills=pills
for
sleeping=pills
which
is
used
for
sleeping

句子是进行时时 前有必动词 后面的动词加ing
例如：I'm playing basketball now.
还有一种情况 动词做名词
例如：Swimming in the river is so exciting.

be动词后面加,现在经行时加,动名词也加,就是动词作主语,举个例子:Eating fruits is good for your health.还有一些其他的,例如Like\Enjoy\Finish

表^现在进行时'时动词后要加ing,还有一些介词后要加,或动词作主语时也加

动词后面加ing，而且正在进行时。例如：我现在正在看电视，I am watchingTV,now.