Polyallylamine conjugates and applications thereof for biological signal amplification are provided by utilizing the essential amino group of polyallylamine to covalently bind with capture agents and signal molecules having the functional groups selected from a group consisting of —NHS, —CO, —S═O2 and —C═O—C═O. The resulting conjugates having more than one signaling entities can be further implemented for biological expression with enhancing effect on biological signal intensity, such that the sensitivity of detection for the variation between biological interactions is largely increased.