sbi po mains have 45 questions for 60 marks given 1 hr.how tough will be the questions.how should i prepare????

We can't comment on the level of the exam but going by the past years trends it should not be very difficult. You need to choose your questions wisely and leave difficult questions in the first round. If time permits, you can come back to them later. Generally, there are always one or two DI sets which require intensive calculation. You should avoid them in the first round as it might take a lot of time and press the panic button. So no matter what is the level of the paper, question selection remains the key thing.
Best of luck.