The present research aimed to study some biological parameters of  Alosa caspia Caspian Sea in the southeast Mazandaran Province in 2014-2015. A total of 600 samples were examined during this period and data were analyzed using SPSS software. The results showed that the mean fork length and total weight of A. caspia was 24.22 ± 54.2 cm and 167.63 ± 63.59 g, respectively, and the length and weight relationship were as W = 0.0558 FL 2.68 R2 = 0.825 for females and W = 0.0553FL 2.65 R2 = 0.825 for males. The results also showed that the age structure of the fish was about 1-5 years old, with the age group of 2 years (with a mean length of 25 cm and an average weight of 190 g), the most frequent (47%). The female sex ratio of male to female was 1:2. Also, the stage 3 of sexual maturity with the frequency of 45% was the highest in the sample population. According to the results, the average length and weight of the Caspian Sea has increased in recent years, but, on the contrary, the frequency of fish with lower ages has also increased. Therefore, given the important role and importance of these fish in the food resource chain of the Caspian Sea, the conservation has a great importance.