i have solved this using below logic

from odoo import fields, models, api

class SalaryUpdateWizard(models.TransientModel):
    _name = "salary.update.wizard"
    _description = "Salary update wizard"

    def compute_employee_id(self):
        project = self.env['employee.salary'].browse(self._context.get('active_ids'))
        print(project)
        return project
    employee_id = fields.Many2one(comodel_name="employee.salary", string="Employee Name" , default=compute_employee_id)
    salary = fields.Float(string="Salary",)

    def update_salary(self):
        rtn = self.env['employee.salary'].browse(self._context.get("active_ids")).update({'salary': self.salary})
        print(rtn)