I am implementing the SPKI Pinning to my mobile apps and i wonder if the Subject Publish Key will change when I renew it with another CA? I still use the same CSR to generate the cert. People say that the Public Key will be the same if we use the same Certificate Signing Request file (CRS), But I'm not sure if CA is also a factor.
Short answer is: no, it shouldn't change, provided you did things properly.
It is recommended that when you specify a SPKI HTTP header you should provide at least two Subject Public Key Information (SPKI) fingerprint of private keys in your control (one for production and other for backup). Now, as reported here, it is a common practice to specify the SPKI fingerprint of well known CA in the case of private key loss, but it renders HPKP invalid because if the CA is compromised then you are basically saying "trust the CA issued certificates". That is why recommendation is to provide the SPKI fingerprint of your own public keys: one for common usage and another in case of private key loss. Thus, provided you are specifying in the SPKI HTTP header of your own public key, whenever you generate a new certificate with another CA (either with the same CSR or a new one) your public key will be the same and the SPKI will still be valid.