Under steam curing condition, there is significant increment in the porosity of concrete. For the purpose of reducing porosity of steam-cured concrete and improving the durability of steam-cured precast elements, this paper carried out contrastive experiments including two curing condition (steam curing and standard curing), simultaneously considering the effect of different binders type, investigated the porosity change of steam curing and standard curing concretes with mineral admixtures. The corresponding mechanism was also discussed. Results indicated that, taking replace of 30% cement with double-mixing fly ash and silica fume achieves the lowest steam-cured concrete porosity. Steam curing technological measures exert a significant influence on the steam-cured concrete unclosed top suface porosity. For the characteristics of different concrete mixtures, the same steam curing technological measures exert different influence. For the same concrete, adopting appropriate technological measures can greatly decreased the porosity of concrete surface to be exposed, especially for concrete with high water-binder ratio.