According to characteristic of point-line meshing gear and basic law of meshing

a common no meshing backlash equation of point-line meshing gear

a calculation formula about least modification coefficient of straight tooth point-line meshing gear and helical point-line meshing gear are researched.Calculation process is set forth about gear modification coefficient of point-line meshing gear through a example.The process is completed through a software.Three conclusions are gotten about no meshing backlash equation of point-line meshing gear and a calculation formula about least modification coefficient being the same with involute gear’s

calculating least modification coefficient and modification coefficient and helix angle of gear made certain well and truly in closed chart.