The invention provides a flexible DC-containing AC/DC hybrid system power flow alternating iterative computation method, so as to solve the problem of power flow computation of the flexible DC-containing AC/DC hybrid system. The method particularly comprises steps: AC/DC hybrid power grid line and node parameters are acquired, wherein the type and the parameter of a connected transformer valve-side virtual node are determined by a corresponding converter control mode and a set value; DC power flow computation is carried out, and if a DC variable crosses a border, a corresponding column of a DCJacobian matrix is removed; a DC power flow computation result is used to correct the absorption or injection power of the virtual node, AC power flow computation is carried out, and the obtained connected transformer valve-side virtual node and AC bus voltage are used as known quantities for next DC power flow iteration; and whether AC and DC power flows are converged is judged, whether the control angle of the converter and the angular phase difference between virtual node and converter AC bus voltage are smaller than computation precision is judged, if yes, convergence is carried out and operation is exited, or otherwise, DC power flow computation is returned.