Abstract: In order to solve long PN code synchronization acquisition under strong jamming environment, PN code acquisition based on adaptive filter scheme is studied. A new synchronization acquisition decision rule base on adaptive filter weight vector norm is proposed. Compared with the traditional method, the new method provides a higher correct detection probability. Under the above method, a united acquisition algorithm combining smart antenna weight vector and the adaptive filter weight vector is studied, which performance is validated by computer simulation. The result shows that the kind of space-time united acquisition algorithm can effectively realize long PN code acquisition under very low SINR environment.