Aims <p>This study explored the effects of irrigation frequency and biochar application on soil phosphorus form and availability of <i>Panax notoginseng</i>, and tried to propose a irrigation frequency and biochar coupling management strategy suitable for the growth of <i>Panax notoginseng</i>.</p> Methods <p>In the experiment, three irrigation frequencies, and four biochar application levels were set, respectively. Hedley phosphorus fractionation was used to determine the forms of phosphorus, and the Mantel test and partial least squares path model were used to study the transformation of soil phosphorus.</p> Results <p>Compared with I1B0, the content of total phosphorus and available phosphorus in soil under I2B6 treatment was the highest. Soil acid phosphatase activity and neutral phosphatase activity decreased to varying degrees. The activity of alkaline phosphatase and the accumulation of phosphorus components showed an upward trend. Irrigation frequency and biochar application amount could regulate the transformation between soil phosphorus forms. It plays an important role in promoting the transformation between phosphorus pools by positively regulating soil chemical properties and activated the transformation of the inert phosphorus bank to low active phosphorus pool.</p> Conclusions <p>The coupling of irrigation frequency and biochar is beneficial to the transformation of soil phosphorus in <i>Panax notoginseng</i>, and provides a reference for the efficient utilization of phosphorus.</p>