Regarding my new project

I am working as a student.. I am doing a project which based on voice recognition.. we have skate board and using arduino uno R3 we planned to work with.. I have confusions in choosing the right motors because it has to bare upto 60kgs.. for right left navigation can servo be used?? Will my motors bare 60kgs and move as per my command

We don't know what your motors will bear - you haven't told us anything about your motors.

What type of motors should be used so that it will work when the load is 60kgs(ie our human body)

Do you only want to turn a skateboard truck left/right, nothing else?

Only to be working on flat ground? What surfaces? Do wheels need to be able to freely spin? Are you using an actual skateboard or building one? You need to explain what you mean by left/right navigation, skateboards work by putting weight on a side to squish a bushing. There's no part of that calling for a servo. Servo would be considered for turning an axle setup.

Have you resolved the voice recognition part of the project yet ?

When designing a project you need to work with the elementary parts first and only when you have those resolved consider incorporating them into a system

If servo is not advisable.. how to turn the wheels of my skate board?? For voice recognition we use bluetooth module

Show your skateboard.

Well, it depends upon motor specifications that how much kg of torque they can produce if you are using 2 motors then you can use up to 30kg torque motors as both will produce enough torque of 60 kg.
Check for servo motor specifications on net and see for torque they can produce.