Abstract: To find out the most suitable spraying concentration of microbial selenium-enriched fertilizer and its optimal application time for Brassica rapa and provide guidance for the promotion and application of selenium- rich B. rapa in actual production, B. rapa‘Jingyan’was used as the material, 5 different concentrations of microbial selenium-enriched fertilizer (including CK) were sprayed on the crop leaves. The results showed that the weight, leaf width, taproot length, selenium content, soluble protein content and vitamin C content of B. rapa were promoted by the application of microbial selenium-enriched fertilizer. Among them, selenium content was increased by se-enriched fertilizer at 40 mg/L. Plant weight, leaf width, soluble protein content and vitamin C content were increased by se- enriched fertilizer at 13.3 mg/L. Taproot length and soluble protein content were increased by se-enriched fertilizer at 10 mg/L. All in all, the spraying of seenriched fertilizer at low concentration (10 mg/L and 13.3 mg/L) could significantly increase the quality of B. rapa. The most optimal time for fertilizer is one week before harvest.