We explore production mechanism and final state interaction in the pp → nK+Σ+ channel based on the inconsistent experimental data published respectively by COSY-11 and COSY-ANKE. The scattering parameter a > 0 for nΣ+ interaction is favoured by large near-threshold cross section within a nonrelativistic parametrization investigation, and a strong nΣ+ interaction comparable to pp interaction is also indicated. Based on this analysis we calculate the contribution from resonance Δ* (1920) through π+ exchange within resonance model, and the numerical result suggests a rather small near-threshold total cross section, which is consistent with the COSY-ANKE data. With an additional sub-threshold resonance Δ* (1620), the model gives a much better description to the rather large near-threshold total cross section published by COSY-11.