The invention discloses reactive 
phosphorus triazine flame retardant for 
dyeing, and a preparation method and application thereof, which belong to the technical field of 
flame retardants and relate to 
flame retardant for cotton. A molecular structure of the reactive 
phosphorus triazine flame retardant for 
dyeing is OPO3OCLO3OO3PO. The preparation method includes: mixing 
pentaerythritol with dioxane under protection of 
inert gases, dropwise adding 
phosphorus oxychloride at 80 DEG C for two hours, adding two to three drops of 
triethylamine, allowing for reaction for 4-10 hours, cooling, filtering, vacuum-
drying to obtain PEPA after rinsing; and mixing 
cyanuric chloride with reaction 
solvent, adjusting the temperature to 10-20DEG C, initially dropwise adding the PEPA and acid-binding agent, allowing for 
continuous reaction for 6 hours, dropwise adding again the PEPA and the acid-binding agent, allowing for reaction for 6 hours, adding precipitant for 
precipitation after cooling, filtering, rinsing, and 
drying to obtain the fished product. The preparation method is simple, the prepared flame retardant has a 
carbon source, an acid source and a gas source integrated and is higher in 
thermal stability and better in carbon forming performance, and the PEPA and the 
triazine structure are complemented while both being given to full play to the advantages.