A 27 years of long-term experiment was conducted to evaluate the effects of fertilizer and rice straw application on release characteristics of non-exchangeable potassium (K) and its release kinetics in reddish paddy soil. There were 5 treatments in study, namely: CK (without fertilization), NP (N, P fertilizers), NPK (N, P and K fertilizers), NP+RS (NP plus rice straw) and NPK+RS (NPK plus rice straw). The results showed that there were two different phases in change of non-exchangeable K release of each treatment, i. e., the linear increase in the first phase (1-14 h) and slow increase in the second phase (14-796 h). The accumulations of non-exchangeable K release in the long-term K fertilization (NPK, NP+RS and NPK+RS) treatments were higher than those in treatments where no K fertilizer was applied (CK and NP). The accumulations of non-exchangeable K release were 62.22 mg/kg and 56.12 mg/kg in the treatments where no K fertilizer was applied (CK and NP), while 67.52, 64.41 and 75.33 mg/kg in treatments where K fertilizer were applied (NPK, NP+RS and NPK+RS), respectively. The accumulations of non-exchangeable K release in the treatments with rice straw application (NP+RS and NPK+RS) were significantly higher than those with no application of rice straw (NP and NPK), which may promote the change from the part of soil mineral potassium to non-exchangeable K under long-term application of rice straw. The four kinds of kinetic equations (parabolic diffusion equation, zero-order equation, first-order equation and Elovich equation) were tested for their suitability to describe the release of non-exchangeable K from the five different treatments. The kinetics of non-exchangeable K release for five treatments could better be simulated by Elovich equation. The segmented straight line equation established from two different phases can better explain the mechanism of release kinetics of non-exchangeable in reddish paddy soil.