Abstract: Aiming at the problem of low accuracy of ionospheric delay modelling in the afternoon in network RTK, a deviation correction method for ionospheric correction values based on conditional adjustment is proposed, using the condition that the theoretical closure difference of the three baselines in the triangle with double-difference ionospheric delays is 0, to adjust the ionospheric correction values obtained by modelling, and the scheme of determining the weighting array in the correction process is discussed. The experiments show that the correction algorithm can effectively improve the accuracy of ionospheric correction when the accuracy of the ionospheric correction model is not high, and at the same time, the determination of the weight array based on the ambiguity fixing of the known baselines can achieve a better correction effect, with the maximum value of the deviation of the ionospheric correction value reduced by 58.0 percent and the overall accuracy improved by 51.1 percent.