The time-resolved pump-probe magneto-optical Kerr technique was used to study the GdFeCo films excited by femtosecond laser. The anormalous Kerr loops were observed

owing to the fact that the sample temperature passed through the ferromagnetic compensation temperature and then caused the change of the direction of net magnetic moment. The anormalous Kerr loops

which were obtained under different pump fluence and different amount of pump pulses

were revealed contained accumulation effect from continuous pulses pump and memory effect from external magnetic field history. The origin of anomalous loops was studied in depth. The results were important to further understand the antiferromagnetic coupling property between rare earth sublattice and transition metal sub-lattice in GdFeCo and the mechanism of magnetization reversal.