The scales were used for age determination of mud carp. The mate-rials were collected in Xijiang River from Wuzhou to Guiping in April 1984 to March 1986. It was found that new annual ring began to appear mostly from March to October. The fish matured at 3 years old and the growth rate decreased after matu-ration.The length-weight relationship formula was calculated to be W=1 .1825x10-5L3.1457 and the relationship between the scale length and standard length was expressed to be R=0.01915L-0.005, where W, L and R represent body weight,standard length and scale lenght respectively. The growth of the mud carp in Xi-jiang River corresponds to von Bertalanffy's growth equation:W_t=29504.87(1一e^{-o.o7(t-1.1429)} )³.L_t=971.14(1一e^{-0.07(t-0.1429)}).here W_t is body weight in grams at the age of t, and L_t is standard Length in mm at the age of t.For conservation and enhancement of the breeding population, it is necessary to regulate that the minimum legal harvestable age of this fish should be 3 years old, and size of 250 mm in length and 430 grams in weight.