The invention discloses privacy protection query language PQL and system thereof, comprising PQL statement and system, the system comprises parsing module, query module and noise-injection module; the parsing module comprises lexical analyzer and syntactic analyzer; user inputs PQL statement according to predetermined semantic and syntactic rules, after parsing module receives the PQL statement, lexical analyzer performs error checks on the PQL statement, correct results are sent to syntactic analyzer; the syntactic analyzer performs grammatical and semantic checks on PQL statement, generates a mapping table and a parameter table with correct results; after receiving mapping table, the query module encapsulates the same into SQL statement, and verifies the encapsulated SQL statement; the noise-injection module obtains final query results of the query module, calculates noise injection sensitivity according to parameter table; the invention ensures the data privacy security and satisfies that the injected noise does not affect data availability.