The effects of the feed with different amount of the dried Spirulina platensis and fresh Spirulina platension on the growth and body color changes in Crucian carp have been studied. The result shows that the more the amount of Spirulina platensis in feed is, the longer and weightier the f ish will be, and the brighter the body color of the fish will become. Feeding with fresh Spirulina platensis would make a better ef fect on increasing fish color and body weight than feeding with the Spirulina pander feed. The methods of quant itative measuring body color have also been studied. When the amount of Spirulina platensis in feed increased, black pigment cells and the OD value of the red pigment abstract with acetone in the f ish scale are promoted. So it is realistic to count the black pigment cells and to analyse the OD value of the red pigment for distinguishing the fish color grades.