Age, growth, Feeding habits and reproduction of the mouse fish (Pt-dcasaz) wore studied. Specimens were collected from middle-upstream of the Pearl Rivernear Guiping County, Guangsi Province during May 1979 azd Seember 1980. All of580 fish taken by gill net, the classes of age and Y coxttributed 42.21，38.21，19.21 and 0.38 of the total number respectively. The relation betweenbody length and the scale diameter is described by the equation : L=8+43.30R(r=0.09956). The length-weight relation of the mouse fish is computed from the equation:W=8.225 x 10^-3L^3.374（r=0.9654）. The mouse fish mainly fed an small bonthiinvertebrates such as imaopera Zacustras,CorbiceaZedae aaa,d sponges, aquatic insectsworms and sponges as well as organic detritus. Apart from these,same phaplarktansincluding.BaciZdcaa2orh.aae, C'horoyta and yat were discovered. in the intes-tines uF the fish. The seratio of males to females was 1:1.5. Spawning occured from.April to septem),er. Mininum size of adult female was 22.3 cnl in length and 381.7g in weight, and 20.0 cm in length. and 204.5 g in weight of male. Eighty-four female fish were examined for fecundity number of eggs were 7878---48,880 (average 22,254.7).Regression equations were developed for fecundity vslength and weight respectivelp as fallaws: R=4.5419L^3.6208 and R=40.88W+1209 Overfishing is the marc of declination of fish production in the Pearl,ivarmas nets have been in use. We suggest that the mesh size of gillxzets should be enlarged to ficm. The use of 5cm mesh net must be prohibited