The invention provides a fire resistance limit rapid detection method for phosphorus-based flame retardant treated-wooden fire doors. The detection method includes the following steps that: (1) phosphorus-based flame retardant treated-wooden fire doors with different flame retardant content are selected, and sampling is performed; (2) as for each door, samples to be tested are accurately weighed,and the samples are dissolved with an acidic solution, cooling, filtering, and a constant volume process are performed; (3) a spectrophotometric method is adopted to measure the content of phosphoruspentoxides in the flame retardants and fire doors; (4) a time period from a time point when each of the phosphorus-based flame retardant treated-wooden fire doors with different flame retardant content is ignited to a time point when each of the phosphorus-based flame retardant treated-wooden fire doors with different flame retardant content is gradually burnt, as well as the quality loss and heatrelease rate of each of the phosphorus-based flame retardant treated-wooden fire doors with different flame retardant content are measured, and the linear relationship between the quality loss and the flame retardant content, the linear relationship between the time period from the time point when each of the phosphorus-based flame retardant treated-wooden fire doors with different flame retardant content is ignited to the time point when each of the phosphorus-based flame retardant treated-wooden fire doors with different flame retardant content is gradually burnt, and the flame retardant content, and the linear relationship between the heat release rates and the flame retardant content are obtained; and (5) the flame retardant content in the doors is measured, and the fire ratingsof the fire doors to be tested can be obtained. The method has the advantages of low cost and high precision.