I have 2001 Honda Odyssey. Lately, whenever I applied brake I feel pulsation on the brake pedal. Is it cause by brake pads or rotor?

Can you also you feel the pulsation in the steering wheel or the body of the car? If it is in the steering wheel then recheck the work that you did. Make sure that the hubs are clear of rust and torque the wheel nuts when putting the tires on.
To check if the rear are bad you can while driving down the road, lightly apply the emergency brake. If you feel the pulsation in the body then it is the rear brakes.
One last test that I have done is clamp off one brake caliper at a time using a clamp on the rubber line and seeing where the pulsation is coming from. Also if the antilock system is engauging there will be a pulsation in the pedal.

Check your rotors, they may need to be turned or replaced.

Is your ABS working properly? Under heavy braking the ABS should engage and 'pulse' the brakes on/off. It is normal to feel the brake petal flutter or pulse under your foot.

Under light braking there should be no pulsing as the ABS does not engage and you have changed the rotors and pads.

Have you checked the rear brakes? They can cause shaking just like the front can.

check rotor and brake pads. also check fluid level. one of those 3 causing problems.
more and likely its the rotor. its cheaper to buy new ones for around 20-30 dollars.
warped rotor will cause the pedal to ..pulsate. and more and likely you pads are wore.
when getting new rotor always put new shoes on so the rotor it can wear evenly.

Could be the inner cup of the cv shaft or the carrier bearing if your vehicle has a halfshaft before the cv axle. If your getting pedal pulsation it must be a bad rotor. Now it should only do it when brakes are applied. Ive seen cases where the pads are very new and the rotor is so warped it will pulsate abd vibrate even withouth applying brakes. Other possobilty is that spindle was damaged and warped/ bent while pressing in new hub bearing.

will try to help. when front wheels shake while applying brakes and you can feel shake in steering wheel, front brakes and rotors need replacement.rotors are warped,if you replace front brake pads, it will return[shaking when you apply brakes] suggest that you replace front rotors[both] replace [both]front brake pads. cost? i would charge [brake pads cost $55.00] labor,$60.00] total $115.00 thank you for choosing fixya.com

The most common cause of brake pulse is wheel bearings, because the rotor wobbles.
The way to tell is that you will also feel it through the steering wheel, when not applying brakes.
If the rotor wobbles, it will also make the brakes spongey, because the wobble will cause some piston retraction, causing a longer throw when applying.
It is usually the fronts that go bad before the back. And one side before the other, often because a bad seal allowed water in. But you can tell by jacking up and feeling for play.

If not a wheel bearing, then I would consider ABS problem, or the rotor was installed wrong.

If you can feel the pedal pulsating and the light turns on the Abs is doin its job. if you want a better stop you could try a brake pad upgrade to ceramic pads and for even more stoping power add an after market drilled and sloted rotors.

If the new rotors were not allow to seat after replacement they will warp extremely easily. Easy to check. Remove wheel and check for trueness of rotor, a dead give away is if you see a blueish tint on the rotor.