We consider a single server retrial model under constant retrial rate policy. The system involves two non-equivalent classes of customers arrived in Poisson input with corresponding class dependent rate. The first class have so called preemptive or high priority, while the second class has low priority. Namely if high priority new arrival enters the system and finds the server busy by the other class, the low priority customer interrupts its service and joins the end of corresponding orbit queue. Relying on Markov Chain method for two-component processes, we obtain necessary stability condition and stability criterion for the model under consideration. The presented analysis is applicable for the general models with non-exponential distribution of service times.