The invention discloses a tie line power flow adjusting method and device for data splicing of internal and external power network of a power system which can be used in a power system to avoid the problem of slow calculation speed and excessive adjustment of some nodes by solving the linear equations of aggregation node adjustment and connection channel power flow deviation. The minimal norm least square solution of ill-conditioned equations can avoid the problem that linear equations have no solution. Considering the limit value of node power adjustment when allocating the node power adjustment, the node power exceeding the limit can be avoided. The whole network power flow calculation data formed by the invention can meet the requirements of online safety and stability analysis calculation speed and accuracy.