If your car is shaking or vibrating when you brake, it could be the result of a few different problems. To find the cause of the shaking, first check the condition of your brake pads and rotors. If the brake pads are worn or warped, they will need to be replaced. In addition, worn rotors can cause brake vibrations, so it's important to check them as well. Before you go any further, it's best to have a trained mechanic inspect your brakes and make sure there are no other issues that could be affecting your car's performance.
If your brake pads and rotors are worn, then they need to be replaced. You can either have a mechanic do the work for you, or replace them yourself with the proper tools. Either way, be sure to purchase quality parts and get the job done right. After the new pads and rotors have been installed, do a test drive to make sure the shaking has stopped.
The shaking may also be caused by misaligned wheels or worn suspension components. Measure the wheel alignment and inspect the shocks and struts for any signs of wear. You can also have the wheels balanced at a tire shop to help reduce vibrations while you drive.
On some cars, the anti-lock braking system (ABS) can cause the brakes to shake if it is malfunctioning. In this case, the ABS control module will need to be diagnosed and possibly replaced to fix the problem.