Cryptography or cryptology is a Greek word it means 'hidden'. It involves the blotting out of the specials meaning of letters, but not their existence. It is the one of the main categories of computer security that converts information from its normal form into an unreadable shape. The art of cryptography has turn more complex in order to make information more secure. The types of cryptography, one is symmetric and another one is asymmetric. Here we discuss about symmetric algorithms briefly. There are many symmetric algorithms are used now a day’s like AES, DES, 3DES, BLOWFISH, RC4, RC6.In this survey we make the blowfish algorithm is more secure to compare other symmetric algorithms.