A simulating experiment was conducted in laboratory to verify the effects of urea, organic-inorganic complex fertilizers and coated organic fertilizers on epilimnion pH values in three types of paddy soils. The results showed that epilimnion pH changed obviously after 5 days of inundated cultivation. There were significant differences in epilimnion pH values between different types of paddy soils during the cultivation. From the 5th day to the 15th day of inundated cultivation, epilimnion pH values increased in all three types of paddy soils under the treatments of CK, coated organic fertilizers and organic-inorganic complex fertilizers; epilimnion pH values decreased slightly in grey fluvo-aquic and saline-sodic paddy soils but increased in red paddy soils under the treatment of urea.