If blood pressure is 170/100 can i still do light walking excercise?

Hopefully you are under care of a doctor for this. As there is not enough information here to give you advice (medications, underlying medical conditions, symptoms, past history of increased blood pressure, and more), I would recommend you ask your physician this question so you can get the best advice possible.

Your pressure is too high for your age. See your PCP for exam and treatment. Walking is good but not the answer, a change in lifestyle is in order.