Abstract: Objective To study the efficacy of IOLP regimen on acute lymphoblastic leukemia（ALL） and its safety. Methods Thirteen patients with ALL were treated with IOLP regimen to observe its efficacy on ALL,recovery time of white blood cells（WBC） and platelets（PLT）,and its hematological toxicity. Results Of the 13 patients after one course of treatment,10（76.9%） had complete remission（CR）,2（15.4%） had partial remission（PR） and 1（7.7%） had no remission（NR）.Of the 13 patients after two courses of treatment,12（92.3%） had CR,1（7.7%） had PR,1（7.7%） had NR.The median time for WBC and PLT to increase to 1.0×10⁹/L and 20×10⁹/L was 17d and 20.5d,respectively.The minimum median number of WBC and PLT was 0.35×10⁹/L and 15×10⁹/L,respectively.Infection occurred in 9 patients（69.2%）.The non-hematological toxicological reactions included mild digestive canal response,transit elevation of transaminase,incidental abnormal heart function,and elevation of BUN. Conclusion The IOLP regimen is significantly effective against ALL with a high remission rate for risk cases and a lower non-hematological toxicity.