Abstract: The effects of plant density on population yield and economic output value in maize and soybean intercropping were studied with the design of the double saturated Doptimal regression. A mathematical model was developed, in which the densities of maize and soybean were independent variables, and population grain yield, dry matter accumulation and economic output value were dependent variables, respectively. The result showed that the plant density significantly affected the population grain yield, dry matter accumulation and economic output value, and the effects of density of maize on population indices were greater than those of density of soybean. Under the low level conditions of density, the population grain yield, dry matter accumulation and economic output value increased with the density of maize and soybean. The maximum population grain yield was 8101.31 kg·hm^-2 with the optimized combination of 72023 plant maize·hm^-2 and 99924 plant soybean·hm^-2, while the maximum population dry matter accumulation was 15282.45 kg·hm^-2 with the optimized combination of 75000 plant maize·hm^-2 and 93372 plant soybean·hm^-2, and the maximum population economic output value was 23494.50 Yuan·hm^-2 with the optimized combination of 73758 plant maize·hm^-2 and 87597 plant soybean·hm^-2. The optimum combination of densities of maize and soybean calculated by computer were 58554-71547 plant·hm^-2 for maize and 82217-100303 plant·hm^-2 for soybean in order to obtain grain yield greater than 7500 kg·hm^-2, dry matter accumulation greater than 14250 kg·hm^-2 and economic output value greater 22500 yuan·hm^-2 under the condition of this experiment.