The social cost of agricultural transfer population citizenization is decomposed into three dimensions: individual livelihood costs, government public service costs, and employers’ labor reproduction security costs. This study measures the citizenization costs of typical migrant workers from both theoretical and practical perspectives. Empirical results show that from 2017 to 2022, Wuhan’s migrant worker citizenization incurred a per capita theoretical total cost of 148 860 yuan, with individual, government, and employer shares at 780 346.76 yuan, 56 663.76 yuan, and 13 849.51 yuan respectively. The actual total investment cost for typical migrant workers was 83 734.45 yuan, including 32 914.80 yuan (individual), 36 062.05 yuan (government), and 14 757.60 yuan (employer) in 2022. The actual cost compliance rates were 37.91% (individual), 67.40% (government), 87.72% (employer), with an overall compliance rate of 53.28%. The theoretical cost-sharing structure is 55.25% (individual), 34.05% (government), and 10.70% (employer), while the actual structure is 39.31% (individual), 43.07% (government), and 17.62% (employer). Sensitivity analysis indicates significant sensitivity to income fluctuations but insensitivity to social security contribution base and housing price changes. Current cost-sharing reveals substantial investment gaps across all three parties, with inadequate alignment between actual inputs and theoretical responsibilities. Mobilizing tripartite investment initiatives—particularly enhancing migrant workers’ capacity and willingness to invest—remains critical for advancing citizenization.