Abstract: Theoretical research on betavoltaic batteries require calculating characteristic parameters of the radiation-voltage conversion device, in order to predict the output characteristics under irradiation. Through the calculated output characteristics, important theoretical references for the design of betavoltaic batteries are provided. Our algorithm calculates the characteristic parameters of the radiation-voltage conversion device based on the tested dark current-voltage curve and evaluates the quality of the characteristic parameters by statistical methods. To prove the effectiveness of the algorithm, the current-voltage curves under irradiation were predicted, and compared with those obtained by exposing to a real radioactive source. Calculation results achieved good results in both curve fitting and output characteristic prediction of the radiation-voltage conversion device. The results show our algorithm can predict the output of betavoltaic battery through the dark current-voltage curve without irradiation and provide guidance for the design of batavoltaic batteries.