In interviews what is more preferable, written test then call those who pass the written test for oral interview or just direct oral interview?

As per my view your given method in not much suitable for manpower hiring. Companies need the strong people in verbal and technically. many candidate are technically strong and able to give good output, but not have bookish statement or definition. there are other issues in written test like if the company located in different city or country the it will be a typical task to conduct the interview for those candidates who resides at other corner. Direct interview is good method.