We report the observation of Bose-Einstein condensation in a dilute 87Rb gas with 1×10\+8 atoms loaded into a quadrupole-Ioffe-configuration trap. After 19s of evaporative cooling, the phase transition condition was achieved. At high phase-space density, diffraction of a probe laser beam was observed. After reducing the trap potential to adiabatically relax the cold atoms we obtained absorption images. A double Gaussian distribution fitted to the data showed the BEC phase transition. The temperature of the transition was about 250nK, and the number of condensate atoms about 5×10\+4.