Objective To design a radiotherapy planning and managing system for calculating the radiotherapy dosage and managing the medicine information of patients in conventional treatment. Methods Visual FoxPro8.0 programming language was used to design the database. The dosimetric factors of linear accelerators were achieved with 3D water tank and dose meter, then Linear interpolation was used for calculating the dose. Results The parameter tables of 3 linear accelerators were set up in the treatment planning module. By analyzing the relations among the parameters, we could calculate the monitor units quickly and accurately. By using of the management module we could realize the archiving, querying and analyzing statistically of radiotherapy information. Conclusion The radiotherapy planning and managing system simplifies operation and reduces  human errors, improves the efficiency as well.