Purple leaf mustard is a new type of healthy vegetable，rich in anthocyanins．Based on the purple-green leaf mustard near isogenic lines（NILs），this paper studied the microscopic distribution and content of anthocyanins in purple leaf mustard，and effect of anthocyanins on its photosynthesis．The results demonstrated that anthocyanins in purple leaf mustard were distributed in the upper and lower epidermis of mustard leaves．Under same light radiation intensity or same CO₂ concentration，the net photosynthetic rate of single plant of purple leaf was significantly lower than that of green leaf．The light compensation point，light saturation point and maximum carboxylation rate of single plant with purple leaf were extreme significantly lower than those with green leaf．The electron transport rate and maximum photosynthesis rate of the single plant with purple leaf was significantly lower than those with green leaf．The anthocyanin content in purple leaf mustard was significant or extremely significant negatively correlated to its photosynthesis characteristics as increasing anthocyanin content would reduce photosynthetic efficiency．