Biopesticides are biologically beneficial to the disease and pest control in agricultural production. However, the traditional view is that biopesticides currently lack economy, making the promotion to farmers in developing countries slow. Based on the perspective of production efficiency under stochastic frontier analysis, we took rice farmers in China as an example to demonstrate the economic effects of biopesticide adoption and its heterogeneity in developing countries. The treatment effect model showed that the adoption had indeed led to an increase in farmers’ productivity, and the external factors, such as cooperatives, plot size, and field culture, as well as their attitude, subjective norms, and perceived behavioural control, contribute to the adoption. Nonlinear regression further indicated the adoption dosage had an inverted u-shaped influence on efficiency, which peaked when biopesticide accounted for 50% of total pesticide input. Moreover, according to quantile regression, the marginal effect of its dosage depended on the efficiency distribution; the more backward the production, the greater the marginal change of efficiency caused by a unit use.