Embryonic stem cells (ES cells ) are undifferentiated permanent cell line derived from inner cell mass cells and primordial germ cells of early developing embryos. Some growth factors were needed in culture medium to maintain LJ ES1 growth , proliferation and undifferentiation for a long time culture in vitro. Effects of various factors on the proliferation of LJ ES1 cells were examined by counting the number of multiplied cells in various mediums ( PESM0 -10 ) omitting one or several factors. Furthermore , emphasis was focused on LIF and bFGF factoreffects. LIFnearlyhadnoeffectonproliferationofearlyLJES1,justmaintainingitsundifferentiation,but it had a little effect on late LJES1;bFGF had a significant stimulative effect on the proliferation of LJES1. The number of LJ ES1 increased linearly at lower concentrations up to 2ng/ ml bFGF , a nearly 2 -3 fold increase was obtained ,at higher than 2ng/ ml concentration the proliferation2promoting effect was further enhanced but not significantly. Both sea perch embryo extract (PEE) and sea perch serum (FS ) promoted the proliferation of LJES1,buttheirproliferatingeffectonLJES1was notsosignificantasbFGF. Theadditionof2 -MEreduced the damage of peroxide on LJ ES1 cells , enhanced cell adhesion and promoted cell proliferation.