Abstract: Objective: Because of high water resoluble and short half life, the carboplatin is much limited in the use of treatment in craniocerebral malignant tumor. We manufactured carboplatin polymer microsphere with chitoson as the carrier to improve the treatment effect of carboplatin in craniocerebral malignant tumor. Methods: After careful consideration, we use "idea function" to arrange our manufacture process. We find that the concentration of chitoson, solid time, the type of chitoson structure and mixture speed affect the diameter of microsphere, but the concentration of chitoson and drug proportion affect drug envelopment into the microsphere. Results: Finally our chitoson polymer microsphere which carried 10% carboplatin have a good appearance without drug crystal on surface, have stable structure even after drug released two weeks, have a smooth release curve without any "burst effect". Conclusion: The chitoson polymer microsphere carried with carboplatin we made have a excellent physical quality, powerful controlled release ability and promising clinical future.