Abstract: In order to understand the mycotoxin contamination of dairy feed in Heilongjiang Province, a total of 41 feed raw materials（9 of whole plant corn silage, 7 of sets corn tabletting, 6 of alfalfa, 6 of soybean meal, 3 of Chinese wild rye, 2 of cotton pulp, 2 of wheat bran, 2 of dry lees and soluble content, 1 of wet corn, 1 of corn flour, 1 of shotcrete corn husk, 1 of corn germ meal）,30 TMR samples（13 of secrete milk cow TMR, 5 of dry cow TMR, 4 of early perinatal period TMR, 7 of after perinatal period TMR and 1 of breeding cattle TMR）, and 15 concentrate supplementary feed samples（7 of concentrate supplementary feed for lactating cows, 2 of concentrate supplementary feed for dry cows, 3 of concentrate supplementary feed at perinatal stage and 3 of concentrate supplementary for rearing cattles） from 10 dairy farms in five regions in Heilongjiang Province were collected.Deoxynivalenol（DON）, T-2 toxin（T-2）, ochratoxin A（OTA）, fumonisin（FUM）,zearalenone（ZEN）、aflatoxin B₁（AFB₁）contents in feeds were determined by ELISA.Pheatmap and UpSetR in R-4.1.1 software were used to make heat maps and Venn plots of mycotoxin exposure. The mycotoxin exposure degree ranking and mixed exposure analysis were carried out in feed samples of dairy cows.The results showed that the positive rates of DON and AFB₁ in feed raw materials were 100%. DON and T-2 exceeded the standard; alfalfa and shotcrete corn husk exceeded the standard for DON, and whole corn silage exceeded the standard for T-2.The positive rates of DON and AFB₁ in TMR mixed feed samples were 100%. ZEN exceeded the standard; dry cow TMR exceeded the standard.The positive rates of DON,FUM,ZEN,AFB₁ in concentrate supplementary feed samples were 100%. DON and ZEN exceeded the standard; concentrate supplementary feed for lactating cows exceeded the standard for DON, and concentrate supplementary feed at perinatal stage exceeded the standard for ZEN.In the investigated dairy cow feed samples, the order of mycotoxin exposure was DON＞T-2 ＞ZEN ＞AFB₁ ＞OTA ＞FUM.The feed samples of dairy cows were all exposed to more than 4 mycotoxins, and the most exposed group was the DON-OTA-FUM-ZEN-AFB₁.It indicated that DON, T-2 and ZEN were seriously exposed in the feed of dairy farms in Heilongjiang Province, and the joint exposure of more than four mycotoxins should be strengthened.