To explore the effects of major agronomic traits on the per plant yield of soybean, the grey relation analysis was used to analyze the relationship of the agronomic traits with per plant yield of 6 soybeans in the second Jiwendai of Heilongjiang area. The results showed that, the agronomic traits of high grey relation degree with per plant yield ordinarily were the seed number per plant > effective branch number > effective grain number per plant > 100-seed weight > pod height at bottom > plant height > growth period > stem internodes number, the seed number per plant had the largest influence to per plant yield, the correlation of per plant yield was 0.42, the effective branch number had a second influence to per plant yield, the correlation of per plant yield was 0.39, the number of internodes influence was relatively minor. When breeding variety was prior to choose single plant, the seed number per plant and the effective branch number were higher.