In these days I'm going to design a e bike project. I'm going to use BLDC motor for that. but normally (according to my knowledge) there are two types of BLDC motors. there are, normal BLDC motor and stepper motor. my problem in can I use a Large stepper motor for the e bike?
Stepper motors have very poor maximum RPMs and dreadful torque at high rpm. Also, controlling stepper motors requires a special controller and it's hard to find high amperage controllers. High-amperage stepper motors are also very expensive.
There's really no advantage to using a stepper motor. You don't need its precision (you can tell a stepper to rotate CW 145 degrees then back CCW 32 degrees, but why would you need that in an e-bike).
Go with an appropriate brushless motor.
Stepper motors are generally used for servo (positioning) applications. They work great in Shimano's Di2 electronic derailleurs (obviously a positioner). But your application is straight velocity mode, stick with BLDC.