Rapidly finding some drugs with the same or similar treatment effect has great application value, it can be convenient to find alternative medicines for users such as medical staffs, drugs salesman and patients. To solve this problem, this paper presents a Drug Similarity Computation (DSC) algorithm which is a new technology about drug data sensing. Firstly, combining the user dictionary and waste word lib, the authors effectively extract drug terms from the indication text of drugs by the technology of Chinese word segmentation. Secondly, weighted indication knowledge database is built based on some terms of the similar indications to facilitate computing the similarity among drugs. Thirdly, according to the given input, a drug sub-set with similar treatment effect is gotten by searching weighted indication knowledge database. The presented algorithm sorts all records in this drug sub-set and does some filtering, and recommends some reasonable drugs according to the user's requirements. Experimental analysis shows that the presented algorithm is valid.