Along with the process of urbanization，how rural migrant workers can get in line with the endowment insurance for urban employees to realize higher old-care utility are urgent issues remain to be solved. Since 2015，some areas including Shandong Province have introduced one-time payment policy for endowment insurance，allowing the employees of enterprises，including migrant workers from rural areas，to buy the urban employees’basic endowment insurance through one-time payment. Nonetheless，workers’concern about the circumstance that the total amount of benefits would be lower than the total amount of contributions leads to their unwillingness to buy insurance. This paper primarily aims to depict the risk preference of the insured with limited rationality based on Cumulative Prospect Theory，and calculates the intrinsic value under this conservative estimation. The results indicate that the amount required by the one-time payment policy is still significantly lower than the intrinsic value，even considering the loss aversion and the subjective probability distortion. In addition，after fulfilling the required minimum payment，continuous payment until retirement could further improve the old-care utility.