Why did Yan Shuangying kill Lin Yuxian?

Because Lin Yuxian is the undercover boss who is inserted beside them! In fact, Yan knew about it for a long time, but she didn't break it. Finally, Lin Yuxian killed Zhao Yaqin, so Yan killed him.

Falcon 1949 is a TV series with the theme of the Liberation War, which is directed by Qian, produced by Zhan Jun, acted as producer, starring Guanhua Liang, and jointly produced by Beijing Aikesaiwen Film and Television Culture Production Co., Ltd. and Dongyang Qingyu Film and Television Culture Co., Ltd.

The drama mainly tells the story of the secret service battalion commander Yan's extraordinary courage and wisdom, clever response to the enemy, and cooperation with Ichiro Nakamura, an ordnance manufacturing expert and researcher of the Second Laboratory of the Japanese 73 1 Bacteriology Force, to break the enemy spy organization and win in one fell swoop.