The invention discloses a B-pillar seal strip and car door-window frame mounting structure comprising an elongated B-pillar seal strip, a car door-window frame, an elongated clamping member, and a nail post welded on the car door-window frame. The B-pillar seal strip is provided with fastening holes in the lengthwise direction. The outer end of the nail post is provided with a clamping shoulder. The clamping member is provided with clamping holes in the lengthwise direction, corresponding to the fastening holes. An end port of each clamping hole is provided with a clamping edge. The B-pillar seal strip covers the nail post through the fastening holes. The clamping member is clamped to the nail post through the clamping holes. The B-pillar seal strip is located between the clamping member and the car door-window frame, and the clamping edges are clamped between the clamping shoulder and the B-pillar seal strip. The B-pillar seal strip and car door-window frame mounting structure can be firmly mounted, the seal strip can be tightly attached to car door-window sheet metal, and exposure of the car door-window sheet metal is avoided.