Based on the population floating theory under the Ranis-Fei dual economic structure, this paper designs an econometric model to study the isoquant curve and production factor substitution law. Finally, through the empirical analysis of labor-capital investment in Henan's agricultural production, combined with the principles of isoquant curve model, this paper determines the labor required for a certain scale of investment in agricultural production, and concludes that the fixed assets investment in Henan's agricultural production is not fully utilized, and too much labor is transferred. And this paper makes the corresponding policy recommendations for Henan's macroeconomic development.