With the help of domestic and foreign research achievements, this paper expounds the influence of secondary internal forces generated by post-tensioned statically indeterminate structures on the establishment of member section stresses and the internal force redistribution of continuous beams, and puts forward improved suggestions for calculation. Under the two limit states, considering the lag characteristics of the strain increment of bonded and unbonded prestressing, parameters such as the strain lag coefficient are introduced as the basis for calculating the crack width, stiffness and flexural bearing capacity of beam sections, and suggested values of relevant parameters are proposed.