The firing range of extended range and trajectory correction projectile is the key factor for the projectile to achieve simultaneous impact. In order to study the influence of time control parameter to the firing rangewe established a compound extended range particle trajectory modeland analyzed the influence of the time control parameterssuch as rocket firing time and drag ring openloop timeto the firing range by using digital simulation method. Further morethe fitting functions were established for the influences.A quantitative description method was presented for extended range and trajectory correction projectile to achieve simultaneous impactwhich has important application and reference value.