The invention discloses an electric automobile frequency modulation optimizing control method based on charge state detection. The method comprises the steps that real-time electricity price data and frequency modulation price data of an electric distribution network are obtained; charging load characteristic data of an electric automobile and an SOC curve of the electric automobile are obtained during a charging stage; an electric automobile charging cost model is established by taking the SOC curve of the electric automobile as a constraint condition; a frequency modulation earning model with the electric automobile participating in frequency modulation is established; a user final earning model is established by combining the charging cost model of the electric automobile and the frequency modulation earning model, and an optimal solution of the user final earning model is solved according to the real-time electricity price data and the frequency modulation price data of the electric distribution network; a charging strategy with the electric automobile participating in frequency modulation and an execution controlling the charging strategy are obtained according to the model optimal solution. According to the electric automobile frequency modulation optimizing control method based on the charge state detection, travel demands of a user are met, and charging in the charging stage and the frequency modulation stage of the electric automobile are reasonably distributed, the user can obtain biggest earnings, and the service life loss cost of a battery is effectively reduced.