The invention discloses a semi-flexible-wall sealing system between an adjustable contraction block and a throat block and based on a continuous transonic-speed wind tunnel nozzle section. The sealingsystem has the advantages that a spring is mounted at the lap joint of the adjustable contraction block and the throat block and above the adjustable contraction block, that is to say, the spring isarranged below a flexible sealing plate; the throat block constantly attaches to the flexible sealing plate, the flexible sealing plate is connected with the adjustable contraction block through a cylindrical rotation pair, the position of the flexible sealing plate can be changed along with the change of the profile faces of the adjustable contraction block and the throat block, the executing mechanisms of the adjustable contraction block and the throat block can allow the spring to have automatic compression during the lifting of the adjustable contraction block and the throat block so as toallow the flexible sealing plate to constantly attaches to the throat block, that is to say, the sealing is completed in a self-adaptation manner, sealing of the throat block section is kept constantly, and the sealing system is a self-adaptation elastic sealing system.