For the need to increase effect of volume utilization rate and volume efficiency for roots pump, a new profile with splayed head for involute rotors was created. Firstly, based on the common profile of involute rotor with max shape coefficients, a new profile composed by top concentric arc, splayed arc for light weight,main involute,bottom avoidance arc was built to enhance shape coefficients and volume utilization rate. Secondly, the simplest parameter coordinate equations of main involute were derived, then the two shape coefficients were computed and results were analyzed as an example. All results indicate that along with the half angle of splayed head is from 1° to 6°, the shape coefficient increase rate of the new profile relative to common profile are respectively from 3.45% to 7.99% used in two teeth rotors, and from 4.55% to 10.54% in three teeth rotors; the more teeth number is and the smaller half angle of trapezoid head is, the more outstanding increase effect is; the relative fit error of the new shape coefficients is smaller than 0.02% in two teeth rotors, and smaller than 0.4% in three teeth rotors, fit accuracy is extremely high enough to be used directly; the radial leakage is effectively controlled and higher volume efficiency is provided by the splayed head; outstandingly, the simple structure of the splayed head and avoidance arc head are easy to proces, etc. It is concluded that a new enhancement design is provided for other profile innovation in roots pump.