Mixing conditions such as incorporation sequence of zinc oxide powder, an activator for mercaptobenzothiazole with which green compound of tires for vehicles like trucks or buses acclerates its vulcanization, and temperature andl time of carbon black mixing stage have been changed in order not only to measure both of scorch time and cure rate of the green compound with Mooney viscometer and rheometer and but also to find optimum mixing condition producing a green compound that would proceed successfully without any scorch during calendering and extrusion steps, etc. Since the green compound prepared from adding zinc oxide in the first stage with mixing at 363K for 4 minutes and also treated further in sulfur mixing second stage at 333k for 2 minutes has lengthened the scorch time 10% more and has showed the same cure rate as the others mixed at higher temperature for longer period in the first stage, it is concluded that the above mixing conditions may save the cost of preparing green compound and its premature vulcanization preserving the qualify of the product as mechanical properties from universal tests machine had exhibited.