This disclosure provides mutant genes related to drug resistance and relapse of acute lymphoblastic leukaemia (ALL) and a use thereof, treatment or prevention of drug resistance and relapse of ALL and a use thereof, a use of compound Lometrexol and related inhibitors targeting GART and AITC in prevention and treatment of drug resistance and relapse of ALL, and a kit for evaluation of the risk of drug resistance and relapse of ALL. The mutation gene is a mutant gene of PRPS1. The drug acts on enzymes in purine synthesis pathway and reduces drug resistance and relapse by decreasing the concentration of hypoxanthine. The kit comprises reagents for lysis of sample cells and an instruction. The invention provides a powerful technical means and support for the prevention and treatment of drug resistance and relapse of ALL.