Defects charactistics of low-dose p+ implanted silicon after rapid thermal annealing (RTA) was studied. RTA at 600℃ can activate most implanted ions. The defects in samples after RTA below 800℃ are found mainly the ion-implantation induced damage defects. Dislocations are found in samples after RTA above 800℃. The ion-implantation damage defects and thermal stress during quenching step are responsible for the formation of dislocations. The concentration of defects in 1100℃RTA sample began to increace. Slip dislocations are induced by thermal stress in the wafer.