Abstract: This study investigated the effect of soil nitrogen regulator on soil available nitrogen. The lab test results showed that application of soil nitrogen regulator decreased soil available nitrogen content significantly, which decreased19.81 mg/kg25 days after application. Field experiment indicated that nitrogen regulator applied after topping could decrease dramatically alkaloid content, increase yield output and ratio of middle-upper class, and improve leaf appearance and quality. The best result was observed on treatment with 1500kg/ha+microorganismII.