Taking the Pseudosciaena crocea as an example , the r ise and fall processes of Pseudosciaena crocea resources are described by the me thod of System Dynamics , and based on the discussion on the behaviour of the model resul t , the reasonable increasing scale of the f ishing fleet is given .The method and result in this paper can be taken as reference for our countr y to f ish other kind of fisheries r esour ces rat ional ly .