Can we implement CMMI combined with software project management?

Of Course....CMMI is a Capability Maturity Model Integrated and is about the organisation's Capability as demonstrated by it existing processes procedures and analysis. Software Project Management may be the complete scope of the organisation or may be one of the elements being integrated to demonstrate the full capability of the organisation.

CMMI Level3 is generally the threshold target which shows that the company can provide repeatable outcomes. CMMI Level4 and5 pushes the capapbility a further step in that metrics and statistical analysis are used for the basis of process improvement.