We explore the connection between particle physics and cosmology, with a focus on neutrino related physics. Firstly, we study the neutrino portal dark matter extension of a concrete type I seesaw model. Since the dark matter candidate is superheavy in the model, the graviton mediated production can contribute significantly. To include the gravitational contribution, we study gravitational production in a Higgs portal scalar dark matter model as a prerequisite and then apply the method to neutrino portal dark matter.We then consider an alternative version of type I seesaw model, namely the type Ib seesaw model. Different from the traditional type I seesaw model, the model allow a connection between neutrino physics and dark matter problem at GeV scale and thus can be related to laboratory experiments. In order to explain the baryon asymmetry through leptogenesis, the model is extended with a superheavy right-handed neutrino which helps to realise the type Ib seesaw mechanism effectively at low energy. The model also provide us a new possibility of vector portal dark matter due to its unique nature of heavy Dirac neutrino. Lastly, we explore the connection between physics beyond the standard model and gravitational waves. In the framework of SO(10) grand unified theory, we considered a minimal model explaining fermion masses and mixing and baryon asymmetry, which can be tested by the next generation of gravitational wave detectors as well as neutrino oscillation experiments which will also constrain the proton lifetime. We also explore the possibility of detecting leptoquark through gravitational wave produced during a electroweak first-order phase transition.