The picture posted on Friday showed the mother breastfeeding her child in a subway car with a caption saying that the mother should mind her behaviour and not expose her sexual organs in a public area.
Hundreds of net users reposted the picture and more than 40,000 participated in the discussion of whether it is proper for mothers to breastfeed their children in public.
The NGO later explained in its apology that it believes that mothers should breastfeed with a cover if conditions are suitable and that otherwise mothers should try to face away from others when breastfeeding their children.
"We apologise for posting (the picture) 'Breast-feeding in Beijing subway' and its social impact. We are not against but respect breastfeeding...The purpose of posting the picture is to call for a discussion of whether it is proper to breastfeed in public without any cover," Beijing-based NGO BJtale wrote on its Sina Weibo.
China still lacks public facilities for mothers to nurse their infants, in spite of flash mobs held in some Chinese cities to draw awareness to breastfeeding.
The NGO - a grass-roots organisation that has set up several welfare activities - had deleted all the posts as of the press time and its last post said that it has closed the Sina Weibo account to think over its mistake.