Biological and reproduction characteristics of female big-eye kilka (Clupeonella grimmi) including body weight, fork length, age, gonad development stages, gonad weight, ganado somatic ratio (GSR) were studied. We sampled 808 fish specimens from the Southern Caspian Sea, Babolsar Area during December 2002 to May 2003. Gonad development stages were assessed through tissue sectioning. Results revealed spawning peak to occur in early January. We also measured body weight as 8.88±0.08 grams, fork length as 1.03±0.26 mm, age as 3.610.03 years, gonad development stage as 3.67±0.03, gonad weight as 0.5±0.01 grams and ganado somatic ratio (GSR) as 5.39 ±0.1 in the specimens. Totally, five age classes, dominated by the 4+ years were distinguished while no 1+ year's age class was observed. The abundance of gonad developmental stages 2-5 was 18.19%, 14.60%, 48.89% and 18.32% respectively. Macroscopic (visual) and microscopic (tissue section) observations of oocyte revealed the same results for gonad development