Range gate is an usual anti-jamming technology for laser guidance. Extraction probability of laser jamming signal in range gate is very important to successful jamming. According to the connection and independence between jamming signal and guidance signal in range gate, it was put forward that the joint probability density function was compatible with laser signal extraction in range gate under jamming. The effect of jamming signal in range gate pull off was thought about. The quantitative relation between extraction probability of jamming signal and advance-synchronizing time was simulated in different width range gate by calculational software Matlab. The results show that there is an optimal advance-synchronizing time for a real-time range gate of which width is fixed. Extraction probability of jamming signal is 0.5 , not 1.0, when advance-synchronizing time is zero. The jamming signal is easy to be extracted by range gate when the timing of jamming devices is good or the range gate is wide. Jamming signal extraction probability increases and the width of range gate is insignificant after the range gate is pulled off. The results of laser signal extraction in range gate during once guidance process and tracking target or false target during repetitious guidance process were simulated by Monte-Carlo. It is beneficial to the construction of assessment system of effectiveness about angle deception jamming.