Abstract: The mathematical model of balanced fertilization in Pak-chio vegetable crop is established，and the regression equations in the relationships among the fertilization and yield as well as its profit have been simulated．The marginal anal-ysis indicates that the most suitable fertilization for the highest yield of Pak-chio is 137.12kg／hm² N，and the ratio of N．P₂0₅ and K₂O is 1：0.77：0.98；the most suitable fertilization for the highest profit of Pak-chio is 123.74kg／hm² N，and the ratio of N，P₂0₅ and K₂O is 1：0.85：1．