There are 983 and 1200 hairtail fish (Trichiurus haumela Forskal) used respectivelyfor age analysis and for composition analrsis. Samples were taken in Po Hai and HuangHai in 1962--1963. The results are summarized as follows: 1) The hairtail fish in Po Hai and Huang hai grow rapidly in the same year theyhatched. The body length reaches 72mm about two months after hatching, and at thelength of 190mm the annulus begins to form. Therefore the first annulus obsreved canbe considered as the first true annulus. 2) The relationship between body length (L) and distance of the annulus from thenueleus (R) on the otolith is conformed with the power function curve: L = 36. 84R^{(1. 595x)} 3) The growth of the hairtail fish is as the following cquations: L_t = L_∞[1 - e^-K(t-t₀))].where L_∞ = 501mm; K= 0.438; t_0 = - 0. 0607 W_t = W_∞[1 -e^(K(t-t₀)]³.where W_∞ = 1592g; K= 0. 34; t = - 0.91 The coordinate of the inflexion point being at t = 2. 32 W_t = 471, corresponding to 0.232 W. 4) The Length (L) weight (W) relationship of the hairtail fish is expressed as fol-lows: W = 3. 339×10~(-6)L^(2.8445) 5) It is certain that the monthly changes of the terminal index at each annulusgroup of the otolith form one cycle each year. The terminal margin of the opaque zone(narrow zone) is called the annulus and the formation of the annulus chiefly takes placefrom January to March.