Due to Earth's non-spherical gravity, ISLs (inter-satellite links) within heterogeneous MEO (medium earth orbit) constellations are intermittent and cannot sustain permanent links. These constellations consist of zero-inclination circular orbits and inclined circular orbits at various inclination angles. Additionally, the pointing direction of the ISLs varies dynamically over a wide range. To overcome these difficulties, this research presents a methodological solution comprising two key components. A calculation method for satellite visibility between inclined orbits was investigated. This enables the identification of specific orbital arcs that allow for permanent link establishment. Second, a strategy of J₂ perturbation compensation via semi-major axis adjustment was proposed, and a remote linking method was introduced to establish links at the far end of these identified permanent-link arcs. Collectively, these techniques enable the realization of permanent inter-satellite links throughout the heterogeneous MEO constellation. Simultaneously, perturbation compensation design for reference scenarios yielded multiple semi-major axis offset schemes with equivalent effectiveness. Link performance simulations conducted in STK confirm that, after compensation, the relative positions of the satellites drift only slowly over the long term. As a result, permanent inter-satellite links are achieved in the heterogeneous MEO constellations previously disrupted by non-spherical gravitation, and links can be established at the far end of the permanent-link arcs. Moreover, the pointing range of the inter-satellite links is significantly reduced compared to the uncompensated case.