Molecule-based ferroelectrics are a class of highly desirable intelligent materials for their highly variable physical properties, easy and environmentally friendly processing, especial light weight and mechanical flexibility. 4-Aminopyridinium Perchlorate (APP), used to be known as a pyroelectric below 243 K, is first discovered to be a new molecular ferroelectric in this work, which has a perfect electric hysteresis loops with a large spontaneous polarization of 1.0 mu C/cm(2) and a small coercive field of 0.67 kV/cm below 246 K. Owing to the dramatic changes of the protonated cations and order-disorder of anions, the crystal symmetry of APP transforms from P2(1)/c to P2(1) in this first-order phase transition, which is revealed by other measurements, such as differential scanning calorimetry, heat capacity, dielectric anomalies and Raman spectrum.