Bucket foundation has promising application prospects in offshore engineering. The calculation of penetration resistance is essential to such foundation installation feasibility analysis. The relationship between the calculation methods of penetration resistance of bucket foundation based on soil strength index and cone penetration resistance is established through theoretical derivation. For clay

the side wall penetration resistance coefficient can be determined by the ratio of cohesion factor to resistance coefficient of cone tip; and the tip penetration resistance coefficient can be determined by the ratio of strip foundation bearing capacity coefficient to resistance coefficient of cone tip. For sand

the side wall penetration resistance coefficient is in proportion to the lateral pressure coefficient and interface friction coefficient

and in inverse proportion to the foundation shape factor and surcharge bearing capacity factor; and the tip penetration resistance coefficient is the reciprocal of the foundation shape factor. The theoretical values of penetration resistance coefficient determined by the geological conditions of the North Sea are close to the empirical values

which provides a theoretical basis for the penetration resistance coefficient. According to the geological conditions of seabed in China

the penetration resistance coefficient is also studied.